CAP2 and Sinus bradycardia: For these studies we monitored six (4 cardiomyocyte-specific CAP2-null and 2 control) animals using ECG telemetry and found that all 4 cardiomyocyte-specific CAP2-null mice first developed sinus bradycardia (Fig. 6b) and then died a few days later from complete atrioventricular block (Fig. 6c).