We determined the sequence and timing of inward ventricular wall motion by least-square phase analysis of radionuclide cineangiograms in 10 patients with left bundle branch block (LBBB), five patients with right bundle branch block (RBBB) and 11 patients with normal conduction. All LBBB and RBBB patients had normal coronary arteries and no segmental wall motion abnormalities. The left ventricle (LV) was divided into eight segments and the right ventricle (RV) into three; sequence and timing were scored by three observers. In normal subjects, wall motion begins in either or both ventricles and ends in the LV or both ventricles. In patients with LBBB it begins in the RV and ends in the LV; in patients with RBBB is begins in the LV and ends in the RV or both ventricles. The intraventricular wall motion is also altered in the ventricle ipsilateral to a bundle branch block. In LBBB, the mean time of onset of LV wall motion is delayed 1.9 frames (38 msec), whereas RV wall motion is normal. In RBBB, the onset of RV wall motion is delayed 1.3 frames (26 msec), whereas LV wall motion is not delayed.

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The value of programmable pulse generators for correcting pacing system malfunction without surgical revision was assessed in 293 patients. Twenty-five patients (8.5%) developed malfunctions from one day to 38 months after implant. Of these, 16 or 64% were successfully managed by programming alone, while nine patients required lead repositioning or a new lead. The majority (75%) of isolated pacing and sensing malfunctions were corrected by programming, but programming restored normal pacing function in only one of five patients who had combined sensing and pacing malfunctions which appeared early after pacemaker insertion. We conclude that programmable pulse generators are particularly useful for managing isolated pacing or sensing malfunctions. However, programmability is not a substitute for careful lead placement.