Dilated cardiomyopathy: When having a big heart is a bad thing

Getty ImagesWhile cardiac disease can affect many breeds of dogs, dilated cardiomyopathy (DCM) is a breed-associated risk for Doberman pinschers and is the most common cardiac disorder from which the breed suffers.1-3 Because the prognosis for affected dogs is typically poor,4,5 veterinarians like to know as much as they can about how to treat, manage and prepare owners for what's to come. Keep in mind that Dobermans are overrepresented for the disorder and make an excellent study group, but they are not the only dogs to suffer from DCM.

Quick overview of DCM

Dogs in early stage one of this disease show no clinical signs, and there are no reliable tests to diagnose it at this point in progression. Stage two is one in which the owner doesn't perceive clinical signs, but a veterinarian can diagnose it using electrocardiography, Holter monitoring and other biomarkers.4, 6-9 At this stage, ventricular arrhythmias and/or systolic dysfunction are usually evident, and one third of the patients at this stage die of sudden cardiac death (SCD). If a dog survives long enough, the disease will eventually progress to stage three, which is characterized by congestive heart failure.4 Approximately one-third of dogs with stage-three disease also die of SCD.4,10

Not much research has been done to evaluate factors that might influence prognosis or provide avenues to help avoid SCD. Ventricular tachycardia is thought to be a risk factor for acute death in Dobermans.5,6 Ventricular late potentials detected by signal-averaged electrocardiography may have prognostic value.11 Cardiac enlargement could also play a role in SCD.12

Finding the beat

This study sought to create a framework for prediction of probable cardiac death and thereby determine which patients might benefit most from treatment options and help avoid unnecessary medications, since many cardiac drugs have negative side effects. The study looked at electrocardiogram (ECG) variables and Holter-ECG monitor variables, as well as blood tests such as cardiac troponin (cTnl) and N-terminal prohormone of brain-natriuretic peptide (NT-proBNP) to try to find predictors of cardiac death.

The study group consisted of 95 affected Dobermans. Forty-one died within three months of their last cardiac examination (SCD group) and were compared with the 54 affected dogs that were still alive one year after study completion. ECG variables and cTnl and NT-proBNP were compared for both groups.

The study found that dogs suffering from an enlarged heart (as calculated by left ventricular end-diastolic volume (LVEDV)/body surface area) was the variable with the most statistically significant prognostic potential in predicting SCD. Other variables (tachycardia, increased cTnl) were not statistically significant themselves, but when combined in a diagnostic tree, could be additional prognostic indicators for risk assessment.

Exam-room application

If you're managing a patient with DCM in your hospital, this study's results indicate that the "easiest" tests, such as NT-proBNP and cTnl, are less able to predict SCD than heart enlargement (as assessed by LVEDV/body surface area). If you are unable to obtain and calculate this value, it may be worth your while to refer to someone who can, as the findings are statistically significant. However, measurement of NT-proBNP and cTnl concentrations could be additional important variables to help predict cardiac enlargement.

Klüser L, Holler PJ, Simak J, et al. Predictors of sudden cardiac death in Doberman pinschers with dilated cardiomyopathy. J Vet Intern Med 2016;30:722-732.

Link to full study: http://onlinelibrary.wiley.com/doi/10.1111/jvim.13941/epdf

References

Wess G, Schulze A, Butz V, et al. Prevalence of dilated cardiomyopathy in Doberman Pinschers in various age groups. J Vet Intern Med 2010;24:533-538.

O'Grady MR, Horne R. The prevalence of dilated cardiomyopathy in doberman pinschers: a 4.5 year follow-up (abstract). J Vet Intern Med 1998;12:199.

Calvert CA. Dilated congestive cardiomyopathy in Doberman pinschers. Compend Contin Educ Vet Pract 1986;8:417-430.

O'Grady MR, O'Sullivan ML. Dilated cardiomyopathy: an update. Vet Clin North Am Small Anim Pract 2004;34:1187-1207.

Calvert CA, Hall G, Jacobs G, et al. Clinical and pathologic findings in Doberman pinschers with occult cardiomyopathy that died suddenly or developed congestive heart failure: 54 cases (1984-1991). J Am Vet Med Assoc 1997;210:505-511.

Calvert CA, Jacobs G, Pickus CW, et al. Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with echocardiographic abnormalities. J Am Vet Med Assoc 2000;217:1328-1332.

Singletary GE, Morris NA, Lynne O'Sullivan M, et al. Prospective evaluation of NT-proBNP assay to detect occult dilated cardiomyopathy and predict survival in Doberman Pinschers. J Vet Intern Med 2012;26:1330-1336.

Wess G, Simak J, Mahling M, et al. Cardiac troponin I in Doberman Pinschers with cardiomyopathy. J Vet Intern Med 2010;24:843-849.

Wess G, Butz V, Mahling M, et al. Evaluation of N-terminal pro-B-type natriuretic peptide as a diagnostic marker of various stages of cardiomyopathy in Doberman Pinschers. Am J Vet Res 2011;72:642-649.

Calvert CA, Pickus CW, Jacobs GJ, et al. Signalment, survival, and prognostic factors in Doberman pinschers with end-stage cardiomyopathy. J Vet Intern Med 1997;11:323-326.

Calvert CA, Jacobs GJ, Kraus M. Possible ventricular late potentials in Doberman pinschers with occult cardiomyopathy. J Am Vet Med Assoc 1998;213:235-239.

Calvert CA, Meurs KM. Cardiomyopathy in Doberman Pinschers. In: Bonagura JD, Twedt DC, eds. Current veterinary therapy. St. Louis: Saunders Elsevier; 2009;800-803.