Final answer:
The patient's symptoms and diagnostic findings most likely point to hypertrophic cardiomyopathy as the underlying etiology of his cardiomyopathy, characterized by a thickened ventricle, diastolic dysfunction, and preserved ejection fraction.
Step-by-step explanation:
The most likely underlying etiology of the patient's cardiomyopathy is hypertrophic cardiomyopathy. Given the small, thickened left ventricle with rapid early filling and diastolic dysfunction, despite a preserved ejection fraction, this diagnosis is consistent with the signs and symptoms presented.
Hypertrophic cardiomyopathy is characterized by the pathological enlargement of the heart, often without a known cause. In hypertrophic cardiomyopathy, the myocardial hypertrophy can lead to diastolic dysfunction due to the rigidity of the thickened ventricular walls, which restricts the filling during diastole, causing symptoms like fatigue and dyspnea despite a normal or preserved ejection fraction, as seen in the described patient's echocardiogram results. Additionally, the cardiomegaly observed on the CXR and the low voltage observed on the ECG support the diagnosis.
This condition can present with symptoms that overlap with other cardiac or pulmonary conditions. Therefore, distinguishing features such as the pattern of ventricular thickening, absence of valvular disease or ischemia, and specific diastolic filling patterns on echocardiography are essential to arrive at a correct diagnosis.