Acute changes in infranodal conduction time following left ventriculography and sublingual nitroglycerin...

During diagnostic cardiac catheterization for the evaluation of chest pain, His bundle electrograms were obtained in 32 male patients before and 2 to 5 minutes after each of two interventions known to acutely affect left ventricular volume and left ventricular end-diastolic pressure (the injection of 40 to 60 cc of contrast medium during left ventriculography and the administration of 0.4 mg of sublingual nitroglycerin). Changes in left ventricular end-diastolic pressure (18 +/- 6 vs 30 +/- 7 mm Hg, p less than 0.001 following ventriculography and 32 +/- 8 vs 19 +/- 8 mm Hg, p less than 0.005 following nitroglycerin administration) were accompanied by parallel alterations in HQ (48 +/- 8 vs 54 +/- 10 msec, p less than 0.005 following ventriculography and 57 +/- 10 vs 53 +/- msec, p less than 0.005 following nitroglycerin administration), but there were no significant changes in atrioventricular (AV) nodal conduction (AH). Significantly greater changes in HQ were seen in patients with triple-vessel coronary artery disease than in the remainder of the population, although there was clinical and/or ECG evidence of ischemia in only one patient. We conclude that factors other than progression of intrinsic conduction system disease may affect infranodal conduction. HQ should be interpreted cautiously in situations with rapidly changing hemodynamics, especially in patients with severe coronary artery disease.