Novel Dominant-Negative Mutation in Cardiac Troponin I Causes Severe Restrictive Cardiomyopathy

A 30-year-old man with a known history of heart failure with preserved ejection fraction and paroxysmal atrial fibrillation diagnosed at 24 years of age was referred to our service due to progressive heart failure. His history was unremarkable for drug use, travel, occupational exposure, and lung disease and was negative for familial cardiomyopathy. His vitals were 108/72 mm Hg, heart rate 60 beats per minute; jugular venous pressure was elevated with a prominent y-descent and positive hepatojugular reflux, and he had mild peripheral edema. Biochemical analysis revealed plasma brain natriuretic peptide=975 pg/mL, estimated glomerular filtration rate=121 mL/min per 1.73 m2 and hemoglobin=134 g/L. Comparison of previous 12-lead ECGs over the past 3 years revealed progressive right atrial enlargement culminating into atrial fibrillation with his previous ECG showing low voltage QRS complexes associated with incomplete right bundle branch block and right axis deviation (Figure 1A). We optimized his medical therapy which included furosemide, spironolactone, bisoprolol, enalapril, and warfarin. Figure 1. ECG shows normal sinus rhythm, right atrium (RA) enlargement, low voltage QRS complex, right axis deviation, and incomplete right bundle branch block ( Ai ). Twelve-lead ECG of a same patient 3 years later showing progression into atrial fibrillation ( Aii ). Transthoracic echocardiogram showing severe dilation of the left atrium and RA and normal-sized ventricles based on the 4-chamber view with a “D”-shaped septum representative of right ventricular (RV) pressure and volume-overload ( Bi ). There was restrictive left ventricle (LV) filling based on transmitral Doppler filling with the deceleration time=100 ms and E-wave amplitude=135 cm/s ( Bii ). Right atrial hemodynamics showed v-wave only with a prominent y-descent ( Ci ), whereas the left- and right-sided catheterization showed elevated LV and RV filling pressures with a clear separation and a dip and plateau morphology ( Cii ). A thorough series of investigations, including transthoracic echocardiogram, coronary angiogram, invasive hemodynamic cardiac catheterization, endomyocardial …