A new case report suggests that accurate, noninvasive diagnoses of cases of unexplained left ventricular hypertrophy and suspected transthyretin amyloid (ATTR) cardiomyopathy (CM) using technetium-labelled pyrophosphate (99mTc-PYP) cardiac scintigraphy can be complicated by false positives and atypical presentations.
The study, published in the European Heart Journal – Case Reports, recommends that cardiac magnetic resonance (CMR) or endomyocardial biopsy (EMB) be considered in selected cases to achieve a correct diagnosis.
“Despite fulfilling the non-invasive diagnostic criteria for ATTR cardiomyopathy, this patient had an ECG absent for the classic features of cardiac amyloidosis and was too young for the diagnosis of wild-type ATTR,” the authors wrote. “Under the clinically doubtful diagnosis of ATTR cardiomyopathy, further confirmation by CMR and EMB excluded the diagnosis and prevented the patient from unnecessary treatment.”
The case involved a 30-year-old man in China with end-stage renal disease and hypertension who presented with exertional dyspnea. Echocardiography detected left ventricular hypertrophy with an end-diastolic wall thickness of up to 16 mm and 99mTc-PYP cardiac scintigraphy found grade 3 myocardial uptake. A negative TTR gene mutation suggested a diagnosis of wild-type ATTR, but his age casted doubt on the diagnosis.
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Further testing with CMR revealed a T1 myocardial value within the normal range, and an EMB showed negative Congo red staining and no evidence of amyloid deposition. Furthermore, there was no histochemical evidence of transthyretin expression.
These results suggested another diagnosis and prevented the patient from undergoing unnecessary treatment for ATTR CM.
Although 99mTc-PYP cardiac scintigraphy is appealing due to its noninvasive nature, the authors recommend that patients presenting at an atypical age for wild-type ATTR CM or who do not present extracardiac symptoms or classic electrocardiogram features undergo EMB to ensure a proper diagnosis.
Reference
Chang HC, Kuo L, Chung FP, Yu WC. Pitfalls for the non-invasive diagnosis of wild-type transthyretin amyloid cardiomyopathy in a young adult: a case report. Eur Heart J – Case Rep. Published online July 13, 2023. doi:10.1093/ehjcr/ytad308
