The twins described in this case had no radiologic evidence of a congenital anomaly, despite exhaustive testing. The fact that the cardiac rhythms were synchronous was cause for concern, because synchronous heart rhythms in thoracopagus twins have been shown to be consistent with shared cardiac chambers. 2,3 An electrocardiogram demonstrating independent QRS complexes suggests isolated ventricles. We could not find any case in the literature where there was an isolated myocardial bridge that could be separated.Although the ability of individual myocytes to sustain an electrical potential and go through the cardiac cycle has been well described, the ability of shared myocardial tissue to propagate a rhythm between two individual hearts has not. The potential for heart block or other fatal arrhythmias was entertained, because we could not predict the electrophysiologic consequences of separating this tissue. Since the operation, the children have shown no cardiac abnormalities and have remained in sinus rhythm.

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Purpose: Pulmonary hypertension (PH) in the recipient affects survival after heart transplantation. Body mass index (BMI) impacts survival in advanced heart failure patients. We sought to investigate the effect of PH on recipient survival based on BMI. Methods: We evaluated the UNOS registry for all adult heart transplant recipients (HTXR) from 2001 to 2012. Recipients with RVAD or BiVad support or TAH were excluded. Patients were stratified based on their body mass index (BMI in kg/m2) at the time of transplant into BMI < 18.5 (underweight), 18.5-29.9 (normal), 30-34.9 (overweight) and 35-40 (obese). PH was defined as systolic pulmonary artery pressure > 35mmHg. Kaplan-Meier estimates were used to compare survival by PH status, and multivariable Cox proportional hazards model assessed risk of mortality with PH, adjusting for patient demographics. Results: Among 21,617 recipients, 2.6% were UWT, 72.6% normal, 19.9% OVWT, and 4.9% obese with 62.6% having PH. Prevalence of PH varied by BMI group (56.7% underweight, 62.7% normal, 63.7% overweight, & 61.3% obese; p< 0.01). Recipients with PH had higher overall mortality rates (26.5% vs. 24.7%, p< 0.01), similarly to normal BMI patients (25.9% vs. 24.0%, p< 0.01). Kaplan-Meier estimate found survival to vary by PH for all patients (p= 0.03 per Log-rank test) and for those with normal BMI (p= 0.02). In unadjusted models, recipients with PH had greater risk of mortality (HR= 1.06, 95% CI: 1.01-1.12), similarly to normal BMI patients (HR= 1.08, 95% CI: 1.01-1.15). After adjusting for age, gender and race, there was a trend towards greater risk, but it was not significant. Conclusion: PH was found to be significantly different across the BMI groups with lowest rate in the underweight and higher in the overweight and obese groups. Additional conditional survival analyses are required to eliminate other patient characteristics which may influence the development of PH.

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