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Canadian genetic testing guidelines and recommendations for individuals diagnosed with HCM are as follows:
- The main purpose of genetic testing is for screening family members.
- According to the results, at-risk relatives may be encouraged to undergo extensive testing.
- Genetic testing is not meant for confirming a diagnosis.
- If the diagnosed individual has no relatives that are at risk, then genetic testing is not required.
- Genetic testing is not intended for risk assessment or treatment decisions.
- Evidence only supports clinical testing in predicting the progression and risk of developing complications of HCM.
For individuals "suspected" of having HCM:
- Genetic testing is not recommended for determining other causes of left ventricular hypertrophy (such as "athlete's heart", hypertension, and cardiac amyloidosis).
- HCM may be differentiated from other hypertrophy-causing conditions using clinical history and clinical testing.
Although HCM may be asymptomatic, affected individuals may present with symptoms ranging from mild to critical heart failure and sudden cardiac death at any point from early childhood to seniority. HCM is the leading cause of sudden cardiac death in young athletes in the United States, and the most common genetic cardiovascular disorder. One study found that the incidence of sudden cardiac death in young competitive athletes declined in the Veneto region of Italy by 89% since the 1982 introduction of routine cardiac screening for athletes, from an unusually high starting rate. As of 2010, however, studies have shown that the incidence of sudden cardiac death, among all people with HCM, has declined to one percent or less. Screen-positive individuals who are diagnosed with cardiac disease are usually told to avoid competitive athletics.
HCM can be detected with an echocardiogram (ECHO) with 80%+ accuracy, which can be preceded by screening with an electrocardiogram (ECG) to test for heart abnormalities. Cardiac magnetic resonance imaging (CMR), considered the gold standard for determining the physical properties of the left ventricular wall, can serve as an alternative screening tool when an echocardiogram provides inconclusive results. For example, the identification of segmental lateral ventricular hypertrophy cannot be accomplished with echocardiography alone. Also, left ventricular hypertrophy may be absent in children under thirteen years of age. This undermines the results of pre-adolescents’ echocardiograms. Researchers, however, have studied asymptomatic carriers of an HCM-causing mutation through the use of CMR and have been able to identify crypts in the interventricular septal tissue in these people. It has been proposed that the formation of these crypts is an indication of myocyte disarray and altered vessel walls that may later result in the clinical expression of HCM. A possible explanation for this is that the typical gathering of family history only focuses on whether sudden death occurred or not. It fails to acknowledge the age at which relatives suffered sudden cardiac death, as well as the frequency of the cardiac events. Furthermore, given the several factors necessary to be considered at risk for sudden cardiac death, while most of the factors do not have strong predictive value individually, there exists ambiguity regarding when to implement special treatment.
ARVD is an autosomal dominant trait with reduced penetrance. Approximately 40–50% of ARVD patients have a mutation identified in one of several genes encoding components of the desmosome, which can help confirm a diagnosis of ARVD. Since ARVD is an autosomal dominant trait, children of an ARVD patient have a 50% chance of inheriting the disease causing mutation. Whenever a mutation is identified by genetic testing, family-specific genetic testing can be used to differentiate between relatives who are at-risk for the disease and those who are not. ARVD genetic testing is clinically available.
Physical examination
The physical examination is often unremarkable, although an arrhythmia characterized by premature beats may be detected.
Electrocardiogram:
An ECG often shows premature ventricular complexes (PVCs). These typically have an upright morphology on lead II (left bundle branch morphology). This occurs as the ectopic impulses usually arise in the right ventricle. In some case, the ECG may be normal. This is due to the intermittent nature of ventricular arrhythmias, and means that the diagnosis should not be excluded on the basis of a normal ECG.
Holter monitor:
A Holter monitor allows for 24-hour ambulatory ECG monitoring. It facilitates quantification of the frequency and severity of ventricular ectopy, and is important in the management of affected dogs. Boxer breeders are encouraged to Holter their breeding stock annually to screen out affected dogs.
Genetic test:
A genetic test for Boxer cardiomyopathy is now commercially available. The genetic test is not yet accepted as a definitive test and additional diagnostic testing continues to be essential to characterize the phenotype, and to help direct therapeutic interventions.
Echocardiogram:
Echocardiography is recommended to determine if structural heart disease is present. A small percentage of dogs have evidence of myocardial systolic dysfunction, and this may affect the long-term prognosis.
All first degree family members of the affected individual should be screened for ARVD. This is used to establish the pattern of inheritance. Screening should begin during the teenage years unless otherwise indicated. Screening tests include:
- Echocardiogram
- EKG
- Signal averaged EKG
- Holter monitoring
- Cardiac MRI
- Exercise stress test
Due to non-compaction cardiomyopathy being a relatively new disease, its impact on human life expectancy is not very well understood. In a 2005 study that documented the long-term follow-up of 34 patients with NCC, 35% had died at the age of 42 +/- 40 months, with a further 12% having to undergo a heart transplant due to heart failure. However, this study was based upon symptomatic patients referred to a tertiary-care center, and so were suffering from more severe forms of NCC than might be found typically in the population. Sedaghat-Hamedani et al. also showed the clinical course of symptomatic LVNC can be severe. In this study cardiovascular events were significantly more frequent in LVNC patients compared with an age-matched group of patients with non-ischaemic dilated cardiomyopathy (DCM). As NCC is a genetic disease, immediate family members are being tested as a precaution, which is turning up more supposedly healthy people with NCC who are asymptomatic. The long-term prognosis for these people is currently unknown.
Generalized enlargement of the heart is seen upon normal chest X-ray. Pleural effusion may also be noticed, which is due to pulmonary venous hypertension.
The electrocardiogram often shows sinus tachycardia or atrial fibrillation, ventricular arrhythmias, left atrial enlargement, and sometimes intraventricular conduction defects and low voltage. When left bundle-branch block (LBBB) is accompanied by right axis deviation (RAD), the rare combination is considered to be highly suggestive of dilated or congestive cardiomyopathy. Echocardiogram shows left ventricular dilatation with normal or thinned walls and reduced ejection fraction. Cardiac catheterization and coronary angiography are often performed to exclude ischemic heart disease.
Genetic testing can be important, since one study has shown that gene mutations in the TTN gene (which codes for a protein called titin) are responsible for "approximately 25% of familial cases of idiopathic dilated cardiomyopathy and 18% of sporadic cases." The results of the genetic testing can help the doctors and patients understand the underlying cause of the dilated cardiomyopathy. Genetic test results can also help guide decisions on whether a patient's relatives should undergo genetic testing (to see if they have the same genetic mutation) and cardiac testing to screen for early findings of dilated cardiomyopathy.
Cardiac magnetic resonance imaging (cardiac MRI) may also provide helpful diagnostic information in patients with dilated cardiomyopathy.
The principal method to diagnose LVH is echocardiography, with which the thickness of the muscle of the heart can be measured. The electrocardiogram (ECG) often shows signs of increased voltage from the heart in individuals with LVH, so this is often used as a screening test to determine who should undergo further testing.
In a study (2006) carried out on 53 patients with the condition in Mexico, 42 had been diagnosed with another form of heart disease and only in the most recent 11 cases that ventricular noncompation was diagnosed and this took several echocardiograms to confirm. The most common misdiagnoses were:
- dilated cardiomyopathy: 30 Cases
- congenital heart disease: 6 Cases
- ischemic heart disease: 2 Cases
- disease of the heart valves: 2 Cases
- dilated phase hypertensive cardiomyopathy: 1 Case
- restrictive cardiomyopathy: 1 Case
The high number of misdiagnoses can be attributed to non-compaction cardiomyopathy being first reported in 1990; diagnosis is therefore often overlooked or delayed. Advances in medical imaging equipment have made it easier to diagnose the condition, particularly with the wider use of MRIs.
HFpEF is typically diagnosed with echocardiography. Techniques such as catheterization are invasive procedures and thus reserved for patients with co-morbid conditions or those who are suspected to have HFpEF but lack clear non-invasive findings. Catheterization does represent are more definitive diagnostic assessment as pressure and volume measurements are taken simultaneously and directly. In either technique the heart is evaluated for left ventricular diastolic function. Important parameters include, rate of isovolumic relaxation, rate of ventricular filling, and stiffness.
Frequently patients are subjected to stress echocardiography, which involves the above assessment of diastolic function during exercise. This is undertaken because perturbations in diastole are exaggerated during the increased demands of exercise. Exercise requires increased left ventricular filling and subsequent output. Typically the heart responds by increasing heart rate and relaxation time. However, in patients with HFpEF both responses are diminished due to increased ventricular stiffness. Testing during this demanding state may reveal abnormalities that are not as discernible at rest.
There are several sets of criteria used to diagnose LVH via electrocardiography. None of them is perfect, though by using multiple criteria sets, the sensitivity and specificity are increased.
The Sokolow-Lyon index:
- S in V + R in V or V (whichever is larger) ≥ 35 mm (≥ 7 large squares)
- R in aVL ≥ 11 mm
The Cornell voltage criteria for the ECG diagnosis of LVH involve measurement of the sum of the R wave in lead aVL and the S wave in lead V. The Cornell criteria for LVH are:
- S in V + R in aVL > 28 mm (men)
- S in V + R in aVL > 20 mm (women)
The Romhilt-Estes point score system ("diagnostic" >5 points; "probable" 4 points):
Other voltage-based criteria for LVH include:
- Lead I: R wave > 14 mm
- Lead aVR: S wave > 15 mm
- Lead aVL: R wave > 12 mm
- Lead aVF: R wave > 21 mm
- Lead V: R wave > 26 mm
- Lead V: R wave > 20 mm
The following screening tool may be useful to patients and medical professionals in determining the need to take further action to diagnose symptoms:
Athlete's heart is not dangerous for athletes (though if a nonathlete has symptoms of bradycardia, cardiomegaly, and cardiac hypertrophy, another illness may be present). Athlete's heart is not the cause of sudden cardiac death during or shortly after a workout, which mainly occurs due to hypertrophic cardiomyopathy, a genetic disorder.
No treatment is required for people with athletic heart syndrome; it does not pose any physical threats to the athlete, and despite some theoretical concerns that the ventricular remodeling might conceivably predispose for serious arrhythmias, no evidence has been found of any increased risk of long-term events. Athletes should see a physician and receive a clearance to be sure their symptoms are due to athlete’s heart and not another heart disease, such as cardiomyopathy. If the athlete is uncomfortable with having athlete's heart or if a differential diagnosis is difficult, deconditioning from exercise for a period of three months allows the heart to return to its regular size. However, one long-term study of elite-trained athletes found that dilation of the left ventricle was only partially reversible after a long period of deconditioning. This deconditioning is often met with resistance to the accompanying lifestyle changes. The real risk attached to athlete's heart is if athletes or nonathletes simply assume they have the condition, instead of making sure they do not have a life-threatening heart illness.
There are no specific diagnostic criteria for TIC, and it can be difficult to diagnose for a number of reasons. First, in patients presenting with both tachycardia and cardiomyopathy, it can be difficult to distinguish which is the causative agent. Additionally, it can occur in patients with or without underlying structural heart disease. Previously normal left ventricular ejection fraction or left ventricular systolic dysfunction out of proportion to a patient’s underlying cardiac disease can be important clues to possible TIC. The diagnosis of TIC is made after excluding other causes of cardiomyopathy and observing resolution of the left ventricular systolic dysfunction with treatment of the tachycardia.
Specific tests that can be used in the diagnosis and monitoring of TIC include:
- electrocardiography (EKG)
- Continuous cardiac rhythm monitoring (e.g. Holter monitor)
- echocardiography
- Radionuclide imaging
- Endomyocardial biopsy
- Cardiac magnetic resonance imaging (CMR)
- N-terminal pro-B-type natriuretic peptide (NT-pro BNP)
Cardiac rhythm monitors can be used to diagnose tachyarrhythmias. The most common modality used is an EKG. A continuous rhythm monitor such as a Holter monitor can be used to characterize the frequency of a tachyarrhythmia over a longer period of time. Additionally, some patients may not present to the clinical setting in an abnormal rhythm, and continuous rhythm monitor can be useful to determine if an arrhythmia is present over a longer duration of time.
To assess cardiac structure and function, echocardiography is the most commonly available and utilized modality. In addition to decreased left ventricular ejection fraction, studies indicate that patients with TIC may have a smaller left ventricular end-diastolic dimension compared to patients with idiopathic dilated cardiomyopathy. Radionuclide imaging can be used as a non-invasive test to detect myocardial ischemia. Cardiac MRI has also been used to evaluate patients with possible TIC. Late-gadolinium enhancement on cardiac MRI indicates the presence of fibrosis and scarring, and may be evidence of cardiomyopathy not due to tachycardia. A decline in serial NT-pro BNP with control of tachyarrhythmia indicates reversibility of the cardiomyopathy, which would also suggest TIC.
People with TIC display distinct changes in endomyocardial biopsies. TIC is associated with the infiltration of CD68 macrophages into the myocardium while CD3 T-cells are very rare. Furthermore, patients with TIC display significant fibrosis due to collagen deposition. The distribution of mitochondria has found to be altered as well, with an enrichment at the intercalated discs (EMID-sign).
TIC is likely underdiagnosed due to attribution of the tachyarrhythmia to the cardiomyopathy. Poor control of the tachyarrhythmia can result in worsening of heart failure symptoms and cardiomyopathy. Therefore, it is important to aggressively treat the tachyarrhythmia and monitor patients for resolution of left ventricular systolic dysfunction in cases of suspected TIC.
Because several well-known and high-profile cases of athletes experiencing sudden unexpected death due to cardiac arrest, such as Reggie White and Marc-Vivien Foé, a growing movement is making an effort to have both professional and school-based athletes screened for cardiac and other related conditions, usually through a careful medical and health history, a good family history, a comprehensive physical examination including auscultation of heart and lung sounds and recording of vital signs such as heart rate and blood pressure, and increasingly, for better efforts at detection, such as an electrocardiogram.
An electrocardiogram (ECG) is a relatively straightforward procedure to administer and interpret, compared to more invasive or sophisticated tests; it can reveal or hint at many circulatory disorders and arrhythmias. Part of the cost of an ECG may be covered by some insurance companies, though routine use of ECGs or other similar procedures such as echocardiography (ECHO) are still not considered routine in these contexts. Widespread routine ECGs for all potential athletes during initial screening and then during the yearly physical assessment could well be too expensive to implement on a wide scale, especially in the face of the potentially very large demand. In some places, a shortage of funds, portable ECG machines, or qualified personnel to administer and interpret them (medical technicians, paramedics, nurses trained in cardiac monitoring, advanced practice nurses or nurse practitioners, physician assistants, and physicians in internal or family medicine or in some area of cardiopulmonary medicine) exist.
If sudden cardiac death occurs, it is usually because of pathological hypertrophic enlargement of the heart that went undetected or was incorrectly attributed to the benign "athletic" cases. Among the many alternative causes are episodes of isolated arrhythmias which degenerated into lethal VF and asystole, and various unnoticed, possibly asymptomatic cardiac congenital defects of the vessels, chambers, or valves of the heart. Other causes include carditis, endocarditis, myocarditis, and pericarditis whose symptoms were slight or ignored, or were asymptomatic.
The normal treatments for episodes due to the pathological look-alikes are the same mainstays for any other episode of cardiac arrest: Cardiopulmonary resuscitation, defibrillation to restore normal sinus rhythm, and if initial defibrillation fails, administration of intravenous epinephrine or amiodarone. The goal is avoidance of infarction, heart failure, and/or lethal arrhythmias (ventricular tachycardia, ventricular fibrillation, asystole, or pulseless electrical activity), so ultimately to restore normal sinus rhythm.
Therapies that support reverse remodeling have been investigated, and this may suggests a new approach to the prognosis of cardiomyopathies (see ventricular remodeling).
Transient apical ballooning syndrome or Takotsubo cardiomyopathy is found in 1.7–2.2% of patients presenting with acute coronary syndrome. While the original case studies reported on individuals in Japan, Takotsubo cardiomyopathy has been noted more recently in the United States and Western Europe. It is likely that the syndrome previously went undiagnosed before it was described in detail in the Japanese literature. Evaluation of individuals with Takotsubo cardiomyopathy typically includes a coronary angiogram to rule out occlusion of the left anterior descending artery, which will not reveal any significant blockages that would cause the left ventricular dysfunction. Provided that the individual survives their initial presentation, the left ventricular function improves within two months.
The diagnosis of Takotsubo cardiomyopathy may be difficult upon presentation. The ECG findings often are confused with those found during an acute anterior wall myocardial infarction. It classically mimics ST-segment elevation myocardial infarction, and is characterised by acute onset of transient ventricular apical wall motion abnormalities (ballooning) accompanied by chest pain, shortness of breath, ST-segment elevation, T-wave inversion or QT-interval prolongation on ECG. Cardiac enzymes are usually negative and are moderate at worst, and cardiac catheterization usually shows absence of significant coronary artery disease.
The diagnosis is made by the pathognomonic wall motion abnormalities, in which the base of the left ventricle is contracting normally or is hyperkinetic while the remainder of the left ventricle is akinetic or dyskinetic. This is accompanied by the lack of significant coronary artery disease that would explain the wall motion abnormalities. Although apical ballooning has been described classically as the angiographic manifestation of takotsubo, it has been shown that left ventricular dysfunction in this syndrome includes not only the classic apical ballooning, but also different angiographic morphologies such as mid-ventricular ballooning and, rarely, local ballooning of other segments.
The ballooning patterns were classified by Shimizu et al. as Takotsubo type for apical akinesia and basal hyperkinesia, reverse Takotsubo for basal akinesia and apical hyperkinesia, mid-ventricular type for mid-ventricular ballooning accompanied by basal and apical hyperkinesia, and localised type for any other segmental left ventricular ballooning with clinical characteristics of Takotsubo-like left ventricular dysfunction.
In short, the main criteria for the diagnosis of Takotsubo cardiomyopathy are: the patient must have experienced a stressor before the symptoms began to arise; the patient’s ECG reading must show abnormalities from a normal heart; the patient must not show signs of coronary blockage or other common causes of heart troubles; the levels of cardiac enzymes in the heart must be elevated or irregular; and the patient must recover complete contraction and be functioning normally in a short amount of time.
Hypertrophy of the ventricle can be measured with a number of techniques.
Electrocardiogram (EKG), a non-invasive assessment of the electrical system of the heart, can be useful in determining the degree of hypertrophy, as well as subsequent dysfunction it may precipitate. Specifically, increase in Q wave size, abnormalities in the P wave as well as giant inverted T waves are indicative of significant concentric hypertrophy. Specific changes in repolarization and depolarization events are indicative of different underlying causes of hypertrophy and can assist in appropriate management of the condition. Changes are common in both eccentric and concentric hypertrophy, though are substantially different from one another. In either condition fewer than 10% of patients with significant hypertrophy display a normal EKG.
Transthoracic echocardiography, a similarly non invasive assessment of cardiac morphology, is also important in determining both the degree of hypertrophy, underlying pathologies (such as aortic coarction), and degree of cardiac dysfunction. Important considerations in echocardiography of the hypertrophied heart include lateral and septal wall thickness, degree of outflow tract obstruction, and systolic anterior wall motion (SAM) of the mitral valve, which can exacerbate outflow obstruction.
It is not uncommon to undergo cardiopulmonary exercise testing (CPET), which measures the heart's response to exercise, to assess the functional impairment caused by hypertrophy and to prognosticate outcomes.
Despite the grave initial presentation in some of the patients, most of the patients survive the initial acute event, with a very low rate of in-hospital mortality or complications. Once a patient has recovered from the acute stage of the syndrome, they can expect a favorable outcome and the long-term prognosis is excellent. Even when ventricular systolic function is heavily compromised at presentation, it typically improves within the first few days and normalises within the first few months. Although infrequent, recurrence of the syndrome has been reported and seems to be associated with the nature of the trigger.
Diastolic dysfunction must be differentiated from diastolic heart failure. Diastolic dysfunction can be found in elderly and apparently quite healthy patients. If diastolic dysfunction describes an abnormal mechanical property, diastolic heart failure describes a clinical syndrome. Mathematics describing the relationship between the ratio of Systole to Diastole in accepted terms of End Systolic Volume to End Diastolic Volume implies many mathematical solutions to forward and backward heart failure.
Criteria for diagnosis of diastolic dysfunction or diastolic heart failure remain imprecise. This has made it difficult to conduct valid clinical trials of treatments for diastolic heart failure. The problem is compounded by the fact that systolic and diastolic heart failure commonly coexist when patients present with many ischemic and nonischemic etiologies of heart failure. Narrowly defined, diastolic failure has often been defined as "heart failure with normal systolic function" (i.e. left ventricular ejection fraction of 60% or more). Chagasic heart disease may represent an optimal academic model of diastolic heart failure that spares systolic function.
A patient is said to have diastolic dysfunction if he has signs and symptoms of heart failure but the left ventricular ejection fraction is normal. A second approach is to use an elevated BNP level in the presence of normal ejection fraction to diagnose diastolic heart failure. Concordance of both volumetric and biochemical measurements and markers lends to even stronger terminology regarding scientific/mathematical expression of diastolic heart failure. These are both probably too broad a definition for diastolic heart failure, and this group of patients is more precisely described as having heart failure with normal systolic function. Echocardiography can be used to diagnose diastolic dysfunction but is a limited modality unless it is supplemented by stress imaging. MUGA imaging is an earlier mathematical attempt to distinguish systolic from diastolic heart failure.
No one single echocardiographic parameter can confirm a diagnosis of diastolic heart failure. Multiple echocardiographic parameters have been proposed as sufficiently sensitive and specific, including mitral inflow velocity patterns, pulmonary vein flow patterns, E:A reversal, tissue Doppler measurements, and M-mode echo measurements (i.e. of left atrial size). Algorithms have also been developed which combine multiple echocardiographic parameters to diagnose diastolic heart failure.
There are four basic Echocardiographic patterns of diastolic heart failure, which are graded I to IV:
- The mildest form is called an "abnormal relaxation pattern", or grade I diastolic dysfunction. On the mitral inflow Doppler echocardiogram, there is reversal of the normal E/A ratio. This pattern may develop normally with age in some patients, and many grade I patients will not have any clinical signs or symptoms of heart failure.
- Grade II diastolic dysfunction is called "pseudonormal filling dynamics". This is considered moderate diastolic dysfunction and is associated with elevated left atrial filling pressures. These patients more commonly have symptoms of heart failure, and many have left atrial enlargement due to the elevated pressures in the left heart.
Grade III and IV diastolic dysfunction are called "restrictive filling dynamics". These are both severe forms of diastolic dysfunction, and patients tend to have advanced heart failure symptoms:
- Class III diastolic dysfunction patients will demonstrate reversal of their diastolic abnormalities on echocardiogram when they perform the Valsalva maneuver. This is referred to as "reversible restrictive diastolic dysfunction".
- Class IV diastolic dysfunction patients will not demonstrate reversibility of their echocardiogram abnormalities, and are therefore said to suffer from "fixed restrictive diastolic dysfunction".
The presence of either class III and IV diastolic dysfunction is associated with a significantly worse prognosis. These patients will have left atrial enlargement, and many will have a reduced left ventricular ejection fraction that indicates a combination of systolic and diastolic dysfunction.
Imaged volumetric definition of systolic heart performance is commonly accepted as ejection fraction. Volumetric definition of the heart in systole was first described by Adolph Fick as cardiac output. Fick may be readily and inexpensively inverted to cardiac input and injection fraction to mathematically describe diastole. Decline of injection fraction paired with decline of E/A ratio seems a stronger argument in support of a mathematical definition of diastolic heart failure.
Another parameter to assess diastolic function is the , which is the ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity (E'). Diastolic dysfunction is assumed when the E/E' ratio exceed 15.
Current treatment options for Boxer cardiomyopathy are largely restricted to the use of oral anti-arrhythmic medications. The aim of therapy is to minimize ventricular ectopy, eliminate syncopal episodes, and prevent sudden cardiac death. A number of medications have been used for this purpose, including atenolol, procainamide, sotalol, mexiletine, and amiodarone. Combinations can also be used. Sotalol is probably the most commonly used antiarrhythmic at this time. It has been demonstrated that sotalol alone, or a combination of mexiletine and atenolol, results in a reduction in the frequency and complexity of ventricular ectopy. It is likely that these medications also reduce syncopal episodes, and it is hoped this extends to a reduced risk of sudden death. Consequently, antiarrhythmic therapy is typically recommended by veterinary cardiologists for Boxer dogs with ARVC. Although relatively rare, oral antiarrhythmic medications may be proarrhythmic in some dogs; consequently, appropriate monitoring and follow-up is recommended.
The ideal therapy for Boxer cardiomyopathy would be implantation of an implantable cardioverter-defibrillator (ICD). This has been attempted in a limited number of dogs. Unfortunately, ICDs are programmed for humans and the algorithms used are not appropriate for dogs, increasing the risk of inappropriate shocks. In the future, reprogramming of ICDs may allow them to emerge as a viable option in the treatment for Boxer cardiomyopathy.
Prognosis in heart failure can be assessed in multiple ways including clinical prediction rules and cardiopulmonary exercise testing. Clinical prediction rules use a composite of clinical factors such as lab tests and blood pressure to estimate prognosis. Among several clinical prediction rules for prognosticating acute heart failure, the 'EFFECT rule' slightly outperformed other rules in stratifying patients and identifying those at low risk of death during hospitalization or within 30 days. Easy methods for identifying low-risk patients are:
- ADHERE Tree rule indicates that patients with blood urea nitrogen < 43 mg/dl and systolic blood pressure at least 115 mm Hg have less than 10% chance of inpatient death or complications.
- BWH rule indicates that patients with systolic blood pressure over 90 mm Hg, respiratory rate of 30 or fewer breaths per minute, serum sodium over 135 mmol/L, no new ST-T wave changes have less than 10% chance of inpatient death or complications.
A very important method for assessing prognosis in advanced heart failure patients is cardiopulmonary exercise testing (CPX testing). CPX testing is usually required prior to heart transplantation as an indicator of prognosis. Cardiopulmonary exercise testing involves measurement of exhaled oxygen and carbon dioxide during exercise. The peak oxygen consumption (VO2 max) is used as an indicator of prognosis. As a general rule, a VO2 max less than 12–14 cc/kg/min indicates a poor survival and suggests that the patient may be a candidate for a heart transplant. Patients with a VO2 max 35 from the CPX test. The heart failure survival score is a score calculated using a combination of clinical predictors and the VO2 max from the cardiopulmonary exercise test.
Heart failure is associated with significantly reduced physical and mental health, resulting in a markedly decreased quality of life. With the exception of heart failure caused by reversible conditions, the condition usually worsens with time. Although some people survive many years, progressive disease is associated with an overall annual mortality rate of 10%.
Approximately 18 of every 1000 persons will experience an ischemic stroke during the first year after diagnosis of HF. As the duration of follow-up increases, the stroke rate rises to nearly 50 strokes per 1000 cases of HF by 5 years.
Despite increasing incidence of HFpEF effective inroads to therapeutics have been largely unsuccessful. Currently, recommendations for treatment are directed at symptom relief and co-morbid conditions. Frequently this involves administration of diuretics to relieve complications associated with volume overload, such as leg swelling and high blood pressure.
Commonly encountered conditions that must be treated for and have independent recommendations for standard of care include atrial fibrillation, coronary artery disease, hypertension, and hyperlipidemia. There are particular factors unique to HFpEF that must be accounted for with therapy. Unfortunately, currently available randomized clinical trials addressing the therapeutic adventure for these conditions in HFpEF present conflicting or limited evidence.
Specific aspects of therapeutics should be avoided in HFpEF to prevent the deterioration of the condition. Considerations that are generalizable to heart failure include avoidance of a fast heart rate, elevations in blood pressure, development of ischemia, and atrial fibrillation. More specific to HFpEF include avoidance of preload reduction. As patients display normal ejection fraction but reduced cardiac output they are especially sensitive to changes in preloading and may rapidly display signs of output failure. This means administration of diuretics and vasodilators must be monitored carefully.
HFrEF and HFpEF represent distinct entities in terms of development and effective therapeutic management. Specifically cardiac resynchronization, administration of beta blockers and angiotensin converting enzyme inhibitors are applied to good effect in HFrEF but are largely ineffective at reducing morbidity and mortality in HFpEF. Many of these therapies are effective in reducing the extent of cardiac dilation and increasing ejection fraction in HFrEF patients. It is unsurprising they fail to effect improvement in HFpEF patients, given their un-dilated phenotype and relative normal ejection fraction. Understanding and targeting mechanisms unique to HFpEF are thus essential to the development of therapeutics.
Randomized studies on HFpEF patients have shown that exercise improves left ventricular diastolic function, the heart's ability to relax, and is associated with improved aerobic exercise capacity. The benefit patients seem to derive from exercise does not seem to be a direct cardiac effect but rather is due to changes in peripheral vasculature and skeletal muscle, which show abnormalities in HFpEF patients.
Patients should be regularly assessed to determine progression of the condition, response to interventions, and need for alteration of therapy. Ability to perform daily tasks, hemodynamic status, kidney function, electrolyte balance, and serum natriuretic peptide levels are important parameters. Behavioral management is important in these patients and it is recommended that individuals with HFpEF avoid alcohol, smoking, and high sodium intake.
An electrocardiogram (ECG/EKG) may be used to identify arrhythmias, ischemic heart disease, right and left ventricular hypertrophy, and presence of conduction delay or abnormalities (e.g. left bundle branch block). Although these findings are not specific to the diagnosis of heart failure a normal ECG virtually excludes left ventricular systolic dysfunction.
Remodeling of the heart is evaluated by performing an echocardiogram. The size and function of the atria and ventricles can be characterized using this test.