Citations

Left ventricular (LV) performance was studied during mild exercise (100 kg-m/min for 3 minutes) in 19 cases of coronary artery disease (CAD). Each patient suffered from a severe anginal syndrome. None had ventricular aneurysm, cardiomegaly, or clinical heart failure. Mean resting values follow: LV end-diastolic pressure (LVEDP), 19 ± 7 mm Hg; LV systolic pressure (LVSP), 150 ± 16 mm Hg; stroke volume index (SVI), 48 ± 10 ml/beat/m 2 ; and LV stroke work index (LVSWI), 81 ± 19 g-m/m 2 . During exercise LVEDP rose to 30 ± 8 mm Hg ( P ≤0.001) and LVS to 160 ± 20 (not significant [NS]); SVI diminished to 46 ± 11 (NS) and LVSWI, to 76 ± 24 (NS). Patients with decreased or asynchronous areas of LV myocardium identified on cine left ventriculograms had higher mean LVEDPs during exercise than did those with normal ventriculograms (34 ± 10 versus 26 ± 4 mm Hg; P ≤0.05). The difference between responses to exercise of patients who experienced angina during the study and of those who did not was NS. Administration of nitroglycerin reduced the increase in LVEDP during exercise. An abnormality in LV performance-a significant rise in LVEDP without a significant increase in SVI or LVSWI-was observed in 13 of 19 cases of CAD.

At the Mayo Clinic, four patients were seen in whom a ventricular septal defect (VSD) of the atrioventricular (A-V) canal type was associated with an angle of nearly 90° between the intact atrial septum and the ventricular septum. The right atrium overrode the ventricular septum and communicated with both ventricles. A complex, straddling right A-V valve had some attachments in the left ventricle and resembled the common A-V valve of persistent common A-V canal. In three of the patients, a congenital mitral valve deformity also existed. Mild cyanosis probably is not a contraindication to surgical repair in such patients because right atrial blood may enter the left ventricle directly.

The morphology of the sinus and atrioventricular (A-V) nodes of human hearts was studied and connecting pathways between these nodes were sought. The cells of both nodes differed from ordinary atrial and ventricular myocardium in respect to size, shape, number, and arrangement of cytoplasmic organelles. Using the criteria of fiber-to-fiber connection, shown by means of serial histological sectioning, this study confirmed previous reports of three pathways between the sinus and A-V nodes in the human heart. It was not required that these pathways be composed of classic Purkinje-type fibers, though many of the fibers did possess some of the features of Purkinje fibers. While recent evidence reveals that specialized atrial pathways do demonstrate increased conduction velocity, their prime functional significance may be in the facilitation of orderly atrial depolarization, the maintenance of sinus node control of ventricular depolarization under various physiological conditions, and the provision of an orderly "input" into the A-V node, a tissue generally acknowledged to have a low margin of safety.