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.

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.

Among the diagnostic procedures done to determine a cardiomyopathy are:

- Physical exam

- Family history

- Blood test

- EKG

- Echocardiogram

- Stress test

- Genetic testing

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.

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.

Therapies that support reverse remodeling have been investigated, and this may suggests a new approach to the prognosis of cardiomyopathies (see ventricular remodeling).

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.

Cardiomyopathies can be classified using different criteria:

- Primary/intrinsic cardiomyopathies

- Genetic

- Hypertrophic cardiomyopathy

- Arrhythmogenic right ventricular cardiomyopathy (ARVC)

- LV non-compaction

- Ion Channelopathies

- Dilated cardiomyopathy (DCM)

- Restrictive cardiomyopathy (RCM)

- Acquired

- Stress cardiomyopathy

- Myocarditis

- Ischemic cardiomyopathy

- Secondary/extrinsic cardiomyopathies

- Metabolic/storage

- Fabry's disease

- hemochromatosis

- Endomyocardial

- Endomyocardial fibrosis

- Hypereosinophilic syndrome

- Endocrine

- diabetes mellitus

- hyperthyroidism

- acromegaly

- Cardiofacial

- Noonan syndrome

- Neuromuscular

- muscular dystrophy

- Friedreich's ataxia

- Other

- Obesity-associated cardiomyopathy

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

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.

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.

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.

Mortality in HIV-infected patients with cardiomyopathy is increased independently of CD4 count, age, sex, and HIV risk group.

The therapy is similar to therapy for non-ischemic cardiomyopathy: after medical therapy is begun, serial echocardiographic studies should be performed at 4-months intervals. If function continues to worsen or the clinical course deteriorates, a biopsy should be considered.

HAART has reduced the incidence of myocarditis thus reducing the prevalence of HIV-associated cardiomyopathy by about 30% in developed countries. However, the prevalence in developing countries is 32% and increasing as HAART is scarce – not to mention the effects of other risk factors such as high cholesterol and lipid diet. IVIGs can also help patients with HIV-associated myocarditis as mentioned earlier.

Treatment for alcoholic cardiomyopathy involves lifestyle changes, including complete abstinence from alcohol use, a low sodium diet, and fluid restriction, as well as medications. Medications may include ACE inhibitors, beta blockers, and diuretics which are commonly used in other forms of cardiomyopathy to reduce the strain on the heart. Persons with congestive heart failure may be considered for surgical insertion of an ICD or a pacemaker which can improve heart function. In cases where the heart failure is irreversible and worsening, heart transplant may be considered.

Treatment will possibly prevent the heart from further deterioration, and the cardiomyopathy is largely reversible if complete abstinence from alcohol is maintained.

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.

The criteria to diagnose a left bundle branch block on the electrocardiogram:

- The heart rhythm must be supraventricular in origin

- The QRS duration must be ≥ 120 ms

- There should be a QS or rS complex in lead V1

- There should be a notched ('M'-shaped) R wave in lead V6.

The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction.

There are also partial blocks of the left bundle branch: "left anterior fascicular block" (LAFB) and a "left posterior fascicular block" (LPFB). This refers to the bifurcation of the left bundle branch.

The presence of LBBB results in that electrocardiography (ECG) cannot be used to diagnose left ventricular hypertrophy or Q wave infarction, because LBBB in itself results in widened QRS complex, and changes in the ST-T segment consistent with ischemia or injury.

It is estimated that the incidence of PPCM in the United States is between 1 in 1300 to 4000 live births. While it can affect women of all races, it is more prevalent in some countries; for example, estimates suggest that PPCM occurs at rates of one in 1000 live births in South African Bantus, and as high as one in 300 in Haiti.

Some studies assert that PPCM may be slightly more prevalent among older women who have had higher numbers of liveborn children and among women of older and younger extremes of childbearing age. However, a quarter to a third of PPCM patients are young women who have given birth for the first time.

While the use of tocolytic agents or the development of preeclampsia (toxemia of pregnancy) and pregnancy-induced hypertension (PIH) may contribute to the worsening of heart failure, they do not cause PPCM; the majority of women have developed PPCM who neither received tocolytics nor had preeclampsia nor PIH.

In short, PPCM can occur in any woman of any racial background, at any age during reproductive years, and in any pregnancy.

Many factors influence the time course and extent of remodeling, including the severity of the injury, secondary events (recurrent ischemia or infarction), neurohormonal activation, genetic factors and gene expression, and treatment. Medications may attenuate remodeling. Angiotensin-converting enzyme (ACE) inhibitors have been consistently shown to decrease remodeling in animal models or transmural infarction and chronic pressure overload. Clinical trials have shown that ACE inhibitor therapy after myocardial infarction leads to improved myocardial performance, improved ejection fraction, and decreased mortality compared to patients treated with placebo. Likewise, inhibition of aldosterone, either directly or indirectly, leads to improvement in remodeling. Carvedilol, a 3rd generation beta blocker, may actually reverse the remodeling process by reducing left ventricular volumes and improving systolic function. Early correction of congenital heart defects, if appropriate, may prevent remodeling, as will treatment of chronic hypertension or valvular heart disease. Often, reverse remodeling, or improvement in left ventricular function, will also be seen.

Zidovudine is an example of a nucleoside analogue and has been shown to cause: myocarditis and dilated cardiomyopathy as well as an increase in total cholesterol, triglycerides, LDL, HDL and insulin resistance. Protease inhibitors are another group of drugs (e.g. ritonavir) and some of them can cause a range of problems such as: lipodystrophy, atherosclerosis, increase total cholesterol, triglyceride, HDL, LDL, and insulin resistance. Amphotericin B can cause dilated cardiomyopathy, hypertension and bradycardia whereas, Ganciclovir can cause ventricular tachycardia. Interferon-alpha can cause arrhythmia and myocardial infarction/ischemia.

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.

At present, there is no effective specific treatment available for diabetic cardiomyopathy. Treatment centers around intense glycemic control through diet, oral hypoglycemics and frequently insulin and management of heart failure symptoms. There is a clear correlation between increased glycemia and risk of developing diabetic cardiomyopathy, therefore, keeping glucose concentrations as controlled as possible is paramount. Thiazolidinediones are not recommended in patients with NYHA Class III or IV heart failure secondary to fluid retention.

As with most other heart diseases, ACE inhibitors can also be administered. An analysis of major clinical trials shows that diabetic patients with heart failure benefit from such a therapy to a similar degree as non-diabetics. Similarly, beta blockers are also common in the treatment of heart failure concurrently with ACE inhibitors.

A wide variety of treatment modalities are currently recommended including Immunosuppressive agents, intravenous immunoglobulins (IVIG), and antiviral agents although the effectiveness of these treatments are not well established and no specific treatment is available.

Diabetic cardiomyopathy is a disorder of the heart muscle in people with diabetes. It can lead to inability of the heart to circulate blood through the body effectively, a state known as heart failure, with accumulation of fluid in the lungs (pulmonary edema) or legs (peripheral edema). Most heart failure in people with diabetes results from coronary artery disease, and diabetic cardiomyopathy is only said to exist if there is "no" coronary artery disease to explain the heart muscle disorder.