Exercise-Induced Left Bundle Branch Block Resulting in Severe Mitral Regurgitation

Figure 1. Electrocardiogram and Pressure Tracings During Exercise Transition from narrow complex sinus tachycardia to left bundle branch block (LBBB) during exercise at 20 W. AO = aorta; PCW = pulmonary capillary wedge; RA = right atrium.

Figure 2. Pressure Tracings During Exercise PCW acutely and rapidly rose from 17 to 47 mm Hg with v-waves to 69 mm Hg during exercise with the development of LBBB. PA pressure increased proportionately to a mean pressure of 48 mm Hg with large retrograde v-waves in late systole from the left atrium. Cardiac output increased to 6.5 l/min, which is 70% predicted based on the measured change in oxygen consumption. PA = pulmonary artery; other abbreviations as in Figure 1.

Figure 3. Transthoracic Echocardiogram Before and After Exercise Mild MR at baseline converted to severe, symptomatic mitral regurgitation (MR) with posterior leaflet tethering and dyssynchrony with the development of a left bundle branch block (LBBB) at 20 W of exercise.