Interpolated ventricular premature complex
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Usually a premature ventricular complex (PVC or VPC) (identified as a wide QRS complex not preceded by a P wave) are followed by a complete compensatory pause. If they are not followed by a pause and are sandwiched between two normal sinus beats, they are called interpolated premature ventricular complexes. This occurs usually when the heart rate is slow. The impulse following the interpolated VPC may have a prolonged PR interval due to concealed retrograde conduction causing a slow conduction of the subsequent sinus beat through the AV junction. In this case the PR interval of the subsequent beat cannot be assessed as the T wave of the ventricular premature complex masks the P wave. The VPCs have an LBBB (left bundle branch block pattern with positive QRS in V6 and a negative QRS in V1, suggesting a right ventricular origin. This along with the inferior axis of the VPCs suggest origin from the right ventricular outflow tract (RVOT VPC), which are the commonest type of benign VPCs.