Impact of incidental amyloidosis on the prognosis of patients with hypertrophic cardiomyopathy undergoing septal myectomy for left ventricular outflow tract obstruction.

To determine the impact of amyloid on the prognosis of patients with hypertrophic cardiomyopathy (HC), we reviewed outcomes of patients who underwent septal myectomy for HC from March 7, 1996, to October 9, 2012, with amyloid deposits identified in operative specimens. Amyloid subtypes were differentiated by mass spectrometry-based proteomics. The survival rate was compared with that of an age-matched population (2:1) without amyloid who underwent septal myectomy for HC. Sixteen patients (mean age ± SD 71 ± 8 years; 12 men) met study criteria. All 16 had intraventricular peak systolic gradients reduced intraoperatively from 105 ± 53 mm Hg to 3 ± 7 mm Hg (p <0.001). Amyloid deposits in specimens ranged from minimal to mild. Nine patients had senile (transthyretin-type) amyloidosis, 4 had immunoglobulin-associated amyloidosis, 2 had apolipoprotein A4 amyloidosis type, and 1 had serum amyloid A type. There were no deaths before 30 days. Twelve patients had New York Heart Association class III or IV function preoperatively, and at last follow-up (median 3 years), class I or II. Only 1 patient received postoperative amyloidosis treatment. The postoperative survival rate at 2 and 4 years was 100% (n = 11 at risk) and 91% (n = 6 at risk), respectively, similar to that of the age-matched population with HC without amyloid who underwent myectomy (p = 0.13). Patients undergoing septal myectomy for HC who have histologic evidence of mild amyloidosis have early outcomes and midterm survival similar to those of patients with HC without amyloidosis who undergo myectomy. In conclusion, although longer follow-up is necessary, small amounts of amyloid, regardless of subtype, do not confer a poor prognosis on patients with HC who undergo septal myectomy.