Tc^99m PYP Scintigraphy to Diagnose Transthyretin Cardiac Amyloidosis in Patients with Non-ischemic Cardiomyopathy

Introduction: Cardiac transthyretin (ATTR) amyloidosis is an increasingly recognized cardiomyopathy in majority cases presented as restrictive cardiomyopathy. The diagnosis is often delayed mostly because of the false assumption that it is a rare disease. Emerging noninvasive imaging modality such as Tc^99m scintigraphy can provide accurate screening for ATTR. We hypothesized that AATR can be seen in heart failure (HF) patients irrespective of features considered as pathognomonic for cardiac amyloidosis.

Aim: To evaluate prevalence of cardiac ATTR by Tc^99m pyrophosphate (PYP) scintigraphy in patients with HF with reduced (HFrEF, LVEF <40%) and middle range ejection fraction (HFmrEF, LVEF 40-49%).

Methods: Thirty-four (mean age 66.8±13 years, 62% males) patients with HF and LVEF<50% without CAD referred to our Heart Failure clinic where included in this study (23 with HFrEF, 11 with HFmrEF) and underwent echocardiography and planar and SPECT Tc^99m -PYP.

Results: Out of 34 patients 19 patients had NYHA FC I-II and 15 patients NYHA FC III. The mean LVEF was 35±7.7%, mean interventricular septum was 11±2.3 mm, mean posterior wall 9.9±2.3 mm. There were 6 (18%) patients with mildly positive Tc^99m-PYP scan, 11 (32%) patients with strongly positive Tc^99m-PYP scan and 17 (50%) patients with negative Tc^99m-PYP scan. No significant difference was observed in the prevalence of positive Tc^99m-PYP scan between patients with HFmrEF and patients with HFrEF. No statistically significant difference between positive vs. negative scans regarding LVEF and LV end-diastolic diameter was found.

Conclusion: In this pilot study ATTR for the first time has been described in half of the patients with non-ischemic cardiomyopathy. In contrast to a widely accepted notion that cardiac amyloidosis is generally considered to be a condition of preserved EF, normal sized and hypertrophic LV, we found a sizeable proportion of positive Tc^99m-PYP scan among patients with LV dysfunction without typical features of ATTR.