ECG Quiz Answer: Complete heart block and right ventricular hypertrophy
ECG Quiz Answer
Complete heart block and right ventricular hypertrophy: There is significant variation in the PP interval from 720 to 960 ms, indicating exaggerated sinus arrhythmia. RR interval is rather fixed at around 1120 ms. PR interval is varying, overall indicating complete heart block. Right axis deviation of QRS complexes (rS in I, aVL) with tall R waves in V1 and deep S in V5, V6 indicate right ventricular hypertrophy. Tall peaked P waves in inferior leads indicate associated right atrial overload.
R wave height in V1 is 23 mm. Using the formula 5 x R wave height in V1 for pulmonary stenosis, estimated right ventricular systolic pressure would come to 115 mm Hg.
Actually this was not a case of isolated pulmonary stenosis. Double outlet right ventricle (DORV) with ventricular septal defect and severe pulmonary stenosis was noted on echocardiogram. Ventricular septal defect is the only outflow for left ventricular blood in DORV and hence it is an obligatory shunt. For the same reason, it is associated with a loud murmur, unlike in Tetralogy of Fallot where the murmur is soft when there is significant cyanosis.
Beats with long PR interval (3rd, 4th and last in the rhythm strip) will have soft first heart sound. Beats in which P waves fall on the ST segment (anywhere between R and T – electrical systole of the ventricles) will have cannon waves as atrial contraction at that time will find the AV valves in a closed position.