Hello! Thank you for asking on HCM! I understand your concern, and would explain that facing your clinical scenario, a comprehensive differential diagnosis is necessary to be performed, to investigate the reason of shortness of breathing coupled with RBBB and chest discomfort. A careful diagnostic work up including thorough physical examination, besides resting ECG a chest X ay study, a cardiac ultrasound, some lab tests such as complete blood count, CK-MB, Troponin, D-dimer, PCR, etc, are necessary to exclude acute an dangerous disorders like pulmonary embolism, a pneumonia, a heart attack, or any other form of acute chest syndromes. A good evaluation of cardiac performance by ECHO, investigating cardiac function, myocardial kinetics, chamber dimension quantifications, any acute valve disorders, aortic or pericardial abnormalities is of utmost importance. It is helpful to rule out any possible pacemaker complications, too. RBBB is not a reason, but a sign of a possible complications. Hope to have been helpful to you. Greetings! Dr. Iliri