Dilated cardiomyopathy

Today we discussed causes of dilated cardiomyopathy,

Some etiologies of DCM:

1) Ischemia
This is the most common cause of cardiomyopathy in the developed world. Within the category of "initially unexplained" DCM, ischemia is less common, since this is usually the first etiology excluded.

2) Valvular heart disease
Some valvular lesions are compensated chronically by LV dilation- mitral regurgitation and aortic insufficiency are the most common (although NB- MR can follow DCM from dilation itself; this is often termed "functional MR"). End-stage aortic stenosis can also cause DCM

3) Infections
-Viral infections can cause myocarditis, which can lead to DCM. Coxsackie, adeno, echo are the most common. HIV is a recognized as a cause of DCM
-Chagas' disease (a protozoan infection) is most common cause of DCM in Central and South America.
-Lyme disease is associated with cardiac muscle dysfunction, although heart blocks are more common.

4) Toxins
-Alcohol; amount and duration correlate with risk
-Cocaine; may be independent of ischemia
-Anthracycline-based chemotherapy (usually takes a dose of 450mg/M2; each cycle has about 50)

-Trace elements. Rare cause; cobalt, arsenic, mercury... Click here for an interesting "outbreak" of cobalt-induced DCM in Quebec

5) Genetic

6) Peripartum CM- unclear cause; occurs in late pregnancy and early post-partum. Carries relatively good prognosis, but high risk of recurrence in subsequent pregnancies

7) Infiltrative CM's- hemochromatosis, sarcoidosis, amyloidosis

8) Tachycardia-induced cardiomyopathy. Prolonged tachycardia can cause reversible, sometimes severe, LV dysfunction

9) "Stress cardiomyopathy" AKA "Takotsubo" cardiomyopathy:
Rare, but increasingly recognized cause of LV dysfunction, with characteristic apical ballooning on 2D echo. May be associated with ECG changes including ST elevation. Sometimes associated with a stressful event (physiological or psychological); self-resolving. Click here for the origin of this term, the Japanese octopus trap...

In a significant proportion of cases, the cause remains idiopathic.

Links:

Click here for a recent NEJM review of DCM that goes over the evidence base for various pharmacologic and device therapies

Click here for a study looking at underlying causes and prognosis for initially idiopathic dilated cardiomyopathy.