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Exertional Syncope as the Presenting Symptom in Cardiac Amyloidosis

Nelson Chavarria, M.D., Gorgi Kozeski, M.D., Todd Kerwin, M.D.

Introduction:  Amyloidosis is a clinical disorder caused by extracellular deposition of fibrils composed of a variety of low-molecular weight serum proteins. Cardiac involvement in amyloidosis is seen in up to 90% of patients, however less than 5% of these patients present with isolated cardiac disease. Syncope or pre-syncope as a presenting symptom of cardiac involvement is uncommon but particularly ominous, as it is often an indicator of severe cardiac involvement and is associated with a high short-term mortality.

Case Presentation:  The patient is a 55 yo male with history of obesity and sleep apnea, who presents following an episode of exertional syncope and extensive facial injuries. He admits to a 3 month history of progressive SOB and fatigue with minimal exertion. His recent outpatient work-up consisted of a treadmill stress test during which he had near-syncope without any significant arrhythmia noted. Subsequent coronary angiography revealed mild non-obstructive disease. Pulmonary function testing demonstrated moderately reduced total lung capacity and minimally reduced diffusion capacity.
On admission, the electrocardiogram revealed sinus rhythm with RBBB, indeterminate axis, inferior Q-waves, normal voltage. Echocardiogram showed an EF of 45-50%, normal LV chamber size, severe concentric LVH, dilated atria, moderate pulmonary hypertension, and diastolic dysfunction with a restrictive filling pattern. No pronounced “speckling” was noted. The patient experienced recurrent syncope while ambulating in the hallway, without arrhythmia on the monitor. A repeat treadmill stress test, quickly precipitated a near-syncopal episode with profound hypotension and hypoxia seen within 2 minutes of light exercise, normal aumentation of heart rate, and no arrhythmia. In the interim, elevated light chain amyloid was confirmed in urine and serum studies. A cardiac MRI revealed left ventricular and right ventricular hypokinesis, with extensive delayed enhancement of both the atria and ventricles, suggestive of an infiltrative cardiomyopathy. Subsequent endomyocardial biopsy confirmed the presence of interstitial amyloid deposits in the myocardium and intramyocardial small vessels. Bone biopsy further revealed underlying plasma cell proliferation, consistent with multiple myeloma.

Discussion:  Cardiac sequelae of amyloidosis are the result of fibril infiltration into the myocardium.  This creates a restrictive cardiomyopathy (stiff heart) and increased cardiac filling pressures leading to symptoms of exercise intolerance and heart failure. Exertional syncope as the presenting symptom of amyloidosis is uncommon.  Multiple factors are described to contribute to syncope, such as autonomic neuropathy leading to postural hypotension as well as brady- and tachy-arrhythmias.  Our patient only experienced syncope with exertion associated with hypotension and hypoxia, and without arrhythmia or chronotropic incompetence. We hypothesize that the cause of syncope was an inability to augment cardiac output due to severe restriction. The hypoxia likely was the result of intense tissue oxygen extraction. Extensive cardiac involvement was demonstrated by cardiac MRI.

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