The Q wave in precordial electrocardiograms overlying the hypertrophied right ventricle: intracavity leads.

Right ventricular cavity electrocardiograms were obtained in six subjects having qR patterns in V leads made from precordial sites overlying the hypertrophied right ventricle. Four of the six, unlike control subjects, had no initial R wave in the right ventricular cavity; one had only a questionable initial R wave. Simultaneous intracavity and precordial electrocardiograms suggested that the initial Q wave over the hypertrophied right ventricle is due to abnormal depolarization of the interventricular septum, and that the large R wave over the hypertrophied right ventricle is the result of delay in activation of the free wall of that chamber. SEMIDIRECT unipolar electrocardio-graphic leads (V leads) from sites on the precordium overlying the normal human right ventricle usually reveal a QRS pattern characterized by a small initial R wave and a large final S wave (rS pattern*).l When the right ventricle is hypertrophied, V leads obtained from the right precordium may show one of four types of QRS complex2: (1) the normal rS pattern; (2) right bundle branch block; (3) evidence suggesting dilatation but not hyper-trophy of the right ventricle; (4) the QRS pattern which is considered diagnostic of right ventricular hypertrophy. This latter pattern, with which we are primarily concerned, is a qR pattern associated with a QRS of normal duration. Occasionally, there may be seen an rSR or qRs pattern. The Q wave in precordial leads overlying the hypertrophied right ventricle may be quite deep in proportion to the succeeding R wave, resulting in Q: R ratios ordinarily associated with myocardial infarction.2 Since the origin of the Q wave in electro-cardiographic leads from the chest overlying the hypertrophied right ventricle is in consider-* In discussing the QRS complex of the electro-cardiogram, small letters will be used to designate relatively small deflections; capital letters will be used to designate large deflections. able dispute2 it was believed that electrocardio-graphic leads taken from the cavity of the right ventricle in subjects showing such a Q wave might shed light on the mechanism of its production. MATERIAL Six patients having a qR or qRs pattern in electro-cardiographic leads overlying the right ventricle were obtained from the medical wards of the Cin-cinnati General Hospital and from the medical wards of the Veterans Hospital, Dayton, Ohio. All patients had roentgenographic evidence of right ventricular hypertrophy. As controls, right ventricular cavity leads were obtained in three subjects who had rS patterns in precordial leads overlying the …