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.

Diagnosis is typically made via echocardiography. Patients will demonstrate normal systolic function, diastolic dysfunction, and a restrictive filling pattern. 2-dimensional and Doppler studies are necessary to distinguish RCM from constrictive pericarditis. Cardiac MRI and transvenous endomyocardial biopsy may also be necessary in some cases. Reduced QRS voltage on EKG may be an indicator of amyloidosis-induced restrictive cardiomyopathy.

Blood tests routinely performed include electrolytes (sodium, potassium), measures of kidney function, liver function tests, thyroid function tests, a complete blood count, and often C-reactive protein if infection is suspected. An elevated B-type natriuretic peptide (BNP) is a specific test indicative of heart failure. Additionally, BNP can be used to differentiate between causes of dyspnea due to heart failure from other causes of dyspnea. If myocardial infarction is suspected, various cardiac markers may be used.

According to a meta-analysis comparing BNP and N-terminal pro-BNP (NTproBNP) in the diagnosis of heart failure, BNP is a better indicator for heart failure and left ventricular systolic dysfunction. In groups of symptomatic patients, a diagnostic odds ratio of 27 for BNP compares with a sensitivity of 85% and specificity of 84% in detecting heart failure.

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 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.

The following screening tool may be useful to patients and medical professionals in determining the need to take further action to diagnose symptoms:

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.

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.

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.

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.

There is a long asymptomatic lead-time in individuals with ARVD. While this is a genetically transmitted disease, individuals in their teens may not have any characteristics of ARVD on screening tests.

Many individuals have symptoms associated with ventricular tachycardia, such as palpitations, light-headedness, or syncope. Others may have symptoms and signs related to right ventricular failure, such as lower extremity edema, or liver congestion with elevated hepatic enzymes.

ARVD is a progressive disease. Over time, the right ventricle becomes more involved, leading to right ventricular failure. The right ventricle will fail before there is left ventricular dysfunction. However, by the time the individual has signs of overt right ventricular failure, there will be histological involvement of the left ventricle. Eventually, the left ventricle will also become involved, leading to bi-ventricular failure. Signs and symptoms of left ventricular failure may become evident, including congestive heart failure, atrial fibrillation, and an increased incidence of thromboembolic events.

The echocardiogram is commonly used to confirm the diagnosis of MI. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systole. Also, it may detect a dilated left atrium and ventricle and decreased left ventricular function.

Because of inability to obtain accurate images of the left atrium and the pulmonary veins with a transthoracic echocardiogram, a transesophageal echocardiogram may be necessary in some cases to determine the severity of MI.

Abnormal heart sounds, murmurs, ECG abnormalities, and enlarged heart on chest x-ray may lead to the diagnosis. Echocardiogram abnormalities and cardiac catheterization or angiogram to rule out coronary artery blockages, along with a history of alcohol abuse can confirm the diagnosis.

The chest X-ray in individuals with chronic MI is characterized by enlargement of the left atrium and the left ventricle. The pulmonary vascular markings are typically normal, since pulmonary venous pressures are usually not significantly elevated.

Treatment of restrictive cardiomyopathy should focus on management of causative conditions (for example, using corticosteroids if the cause is sarcoidosis), and slowing the progression of cardiomyopathy. Salt-restriction, diuretics, angiotensin-converting enzyme inhibitors, and anticoagulation may be indicated for managing restrictive cardiomyopathy.

Calcium channel blockers are generally contraindicated due to their negative inotropic effect, particularly in cardiomyopathy caused by amyloidosis. Digoxin, calcium channel blocking drugs and beta-adrenergic blocking agents provide little benefit, except in the subgroup of restrictive cardiomyopathy with atrial fibrillation. Vasodilators are also typically ineffective because systolic function is usually preserved in cases of RCM.

Heart failure resulting from restrictive cardiomyopathy will usually eventually have to be treated by cardiac transplantation or left ventricular assist device.

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.

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.

A jugular venous distension is the most sensitive clinical sign for acute decompensation.

Generally, diastolic dysfunction is a chronic process. When this chronic condition is well tolerated by an individual, no specific treatment may be indicated. Rather, therapy should be directed at the root cause of the stiff left ventricle, with potential causes and aggravating factors like high blood pressure and diabetes treated appropriately. Conversely (as noted above), diastolic dysfunction tends to be better tolerated if the atrium is able to pump blood into the ventricles in a coordinated fashion. This does not occur in atrial fibrillation (AF), where there is no coordinated atrial activity and the left ventricle loses around 20% of its output. However, in chronic AF and in geriatric patients, AF is better tolerated and the cardiologist must choose between a stable AF at a lower rate and the risk of having an intermittent AF if he pretends to treat AF aggressively with all the thrombo-embolic risk it implies. In the same light, and also as noted above, if the atrial fibrillation persists and is resulting in a rapid heart rate, treatment must be given to slow down that rate. Usually digoxin maintains a stable rhythm. The use of a self-expanding device that attaches to the external surface of the left ventricle has been suggested, yet still awaits FDA approval. When the heart muscle squeezes, energy is loaded into the device, which absorbs the energy and releases it to the left ventricle in the diastolic phase. This helps retain muscle elasticity.

The role of specific treatments for diastolic dysfunction "per se" is as yet unclear. Diuretics can be useful, if these patients develop significant congestion, but patients must be monitored because they frequently develop hypotension.

Beta-blockers are the first-line therapy as they induce bradycardia and give time for ventricles to fill. There is some evidence that calcium channel blocker drugs may be of benefit in reducing ventricular stiffness in some cases (verapamil has the benefit lowering the heart rate). Likewise, treatment with angiotensin converting enzyme inhibitors, such as enalapril, ramipril, and many others, may be of benefit due to their effect on preventing ventricular remodeling but under control to avoid hypotension.

Cardiac arrest is synonymous with clinical death.

A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse is the gold standard for diagnosing cardiac arrest, as lack of a pulse (particularly in the peripheral pulses) may result from other conditions (e.g. shock), or simply an error on the part of the rescuer. Nonetheless, studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals or lay persons.

Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. The Resuscitation Council (UK), in line with the ERC's recommendations and those of the American Heart Association,

have suggested that the technique should be used only by healthcare professionals with specific training and expertise, and even then that it should be viewed in conjunction with other indicators such as agonal respiration.

Various other methods for detecting circulation have been proposed. Guidelines following the 2000 International Liaison Committee on Resuscitation (ILCOR) recommendations were for rescuers to look for "signs of circulation", but not specifically the pulse. These signs included coughing, gasping, colour, twitching and movement. However, in face of evidence that these guidelines were ineffective, the current recommendation of ILCOR is that cardiac arrest should be diagnosed in all casualties who are unconscious and not breathing normally. Another method is to use molecular autopsy or postmortem molecular testing which uses a set of molecular techniques to find the ion channels that are cardiac defective.

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.

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.

Ischemic cardiomyopathy can be diagnosed via magnetic resonance imaging (MRI) protocol, imaging both global and regional function. Also the Look-Locker technique is used to identify diffuse fibrosis; it is therefore important to be able to determine the extent of the ischemic scar. Some argue that only left main- or proximal-left anterior descending artery disease is relevant to the diagnostic criteria for ischemic cardiomyopathy. Myocardial imaging usually demonstrates left ventricular dilation, severe ventricular dysfunction, and multiple infarctions. Signs include congestive heart failure, angina edema, weight gain and fainting, among others.

The most recent studies indicate that with newer conventional heart failure treatment consisting of diuretics, ACE inhibitors and beta blockers, the survival rate is very high at 98% or better, and almost all PPCM patients improve with treatment. In the United States, over 50% of PPCM patients experience complete recovery of heart function (EF 55% or greater). Almost all recovered patients are eventually able to discontinue medications with no resulting relapse and have normal life expectancy.

It is a misconception that hope for recovery depends upon improvement or recovery within the first six to 12 months of diagnosis. Many women continue to improve or recover even years after diagnosis with continued medicinal treatment. Once fully recovered, if there is no subsequent pregnancy, the possibility of relapse or recurrence of heart failure is minimal.

Subsequent pregnancy should be avoided when left ventricular function has not recovered and the EF is lower than 55%. However, many women who have fully recovered from PPCM have gone on to have successful subsequent pregnancies. A significant study reports that the risk for recurrence of heart failure in recovered PPCM patients as a result of subsequent pregnancy is approximately 21% or better. The chance of relapse may be even smaller for those with normal contractile reserve as demonstrated by stress echocardiography. In any subsequent pregnancy, careful monitoring is necessary. Where relapse occurs, conventional treatment should be resumed, including hydralazine with nitrates plus beta-blockers during pregnancy, or ACE-inhibitors plus beta-blockers following pregnancy.

The prognosis for TIC after treatment of the underlying tachyarrhythmia is generally good. Studies show that left ventricular function often improves within 1 month of treatment of the tachyarrhythmia, and normalization of the left ventricular ejection fraction occurs in the majority of patients by 3 to 4 months. In some patients however, recovery of this function can take greater than 1 year or be incomplete. In addition, despite improvement in the left ventricular ejection fraction, studies have demonstrated that patients with prior TIC continue to demonstrate signs of negative cardiac remodeling including increased left ventricular end-systolic dimension, end-systolic volume, and end-diastolic volume. Additionally, recurrence of the tachyarrhythmia in patients with a history of TIC has been associated with a rapid decline in left ventricular ejection fraction and more severe cardiomyopathy that their prior presentation, which may be a result of the negative cardiac remodeling. There have also been cases of sudden death in patients with a history of TIC, which may be associated with worse baseline left ventricular dysfunction. Given these risks, routine monitoring with clinic visits, ECG, and echocardiography is recommended.