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Abstract & Commentary
By Michael H. Crawford, MD
Source: Doumas A, et al. Prevalence and clinical characteristics of non-dilated cardiomyopathy and the effect of atrial fibrillation. Am J Cardiol. 2010;105:884-887.
Little is known about the least common of left ventricular (LV) remodeling abnormalities, low ejection fraction (EF) with no cavity dilation or non-dilated cardiomyopathy. Thus, these investigators from the Lahey Clinic in Burlington, MA, retrospectively analyzed 98 such patients. To obtain the study population, they reviewed six months of echocardiograms (3,350) and selected those with an EF < 0.45 and a LV diastolic diameter < 5.6 cm. They excluded those with congenital, valvular, coronary disease with wall-motion abnormalities and cardiac amyloid. The prevalence of non-dilated cardiomyopathy in this echocardiographic laboratory population was 14% (98/3,350). One half had a history of hypertension and 43% had atrial fibrillation (AF). Symptoms were more common in those with EF < 30% (37%) vs. > 30% (12%, p < 0.01). Concentric remodeling was present in 41% and LV hypertrophy (mass > 105 g/m2) in 12%. Therefore, increased wall thickness or mass was present in over half. About half the patients had a follow-up echocardiogram (average 422 days later), and the mean EF increased between studies (p < 0.01), mainly in the patients with AF (33% to 39%). The authors concluded that non-dilated cardiomyopathy is often associated with hypertension or AF, and an improvement in EF is seen in the majority during follow-up.
Among those referred to an echocardiographic laboratory with low EF, 14% had no LV dilation, which is similar to another reported experience (20%). In these patients, over half had either increased LV wall thickness or increased LV mass. This could be explained by the 50% incidence of hypertension in these patients, which is similar to other heart-failure trials. However, the incidence of AF in these patients was twice what has been seen in large heart-failure trials (42% vs. 12%-25%). In a retrospective study, it is difficult to tell whether AF is causative or a marker for low EF. We know that unchecked rapid AF can cause reduced LV function (tachycardia-induced cardiomyopathy). This may explain many of these cases, since EF rose over time in the AF subgroup. Perhaps the heart rate was brought under control or AF was eliminated between the two echocardiograms. Regardless, it would appear that there is significant potential for improvement in patients with non-dilated cardiomyopathy and AF.
Those without AF may represent a transition stage between hypertrophy with diastolic dysfunction and early systolic dysfunction before dilation occurs. Against this hypothesis is that in the subgroups with two echoes, no increase in cavity volume was observed. Consequently, this could represent a separate disease state, the etiology of which is unclear, but is probably multifactorial. Interestingly, less than one-quarter were significantly symptomatic, but symptoms were more common in those with EF < 30%. Since the average EF was 34% (range 15%-45%), the number with significant symptoms (NYHA class III-IV) seems low at 22%. Perhaps the lack of LV dilation is associated with lower filling pressures. Unfortunately there is no diastolic function data in the report, and left atrial pressure cannot be estimated from the data given. Until more data on non-dilated cardiomyopathy are forthcoming, the clinical message is that this entity seems to have potential for improvement in LV function. Thus, aggressive therapy should be instituted.