NPPB and atrial flutter: Of 31 symptomatic patients with a predominantly cardiac or mixed phenotype at enrollment, the following were observed: 9 (29%) had atrial fibrillation or atrial flutter at baseline, 18 (58.1%) had conduction abnormalities, 3 (9.7%) had a pacemaker, median LV diastolic diameter was 46 mm, median LV septum diameter was 17 mm, median ejection fraction was 52%, median LV mass index was 186.4 gm/m2, and median N-terminal pro-B-type natriuretic peptide (NT-proBNP) was 2648 pg/mL (Table 3).