AUTONOMIC MANEUVERS IN HEREDITARY Q-T INTERVAL PROLONGATION (ROMANO-WARD SYNDROME)

Since extrinsic autonomic defects have been postulated to be a primary etiologic mechanism in hereditary Q-T interval prolongation, heart rate and Q-T interval responses of three affected members of a family with Romano-Ward syndrome and eight normal volunteers were studied in the control state and after blocking doses of propranolol, atropine, propranolol plus atropine, and trimethaphan, a ganglionic blocking agent. The isoproterenol infusion rate required to increase resting heart rate by 30 per minute was determined. During the control state, cycle length changes in the normal volunteers and affected family members were not appreciably different with respect to: prolongation during carotid sinus pressure and post-Valsalva and shortening during the initial phase of hand-grip. These changes were abolished by atropine but not by propranolol. As compared to the normal volunteers, the affected family members' maximal heart rates during treadmill exercise were similar but after propranolol they were significantly lower. Isoproterenol sensitivity in affected family members was not significantly different from that in normal volunteers. The affected family members tended to have low resting heart rates and manifested abnormally low increments in rate with atropine. Their heart rates were abnormally low after propranolol plus atropine and trimethaphan, without evidence of depressed left ventricular function. When changes in cycle length were accounted for, affected family members' Q-T intervals during the control maneuvers were unaltered by propranolol, trimethaphan, and isoproterenol. However, one affected family member demonstrated disproportionate Q-T interval lengthening and alternation in T or U wave amplitude with the lowest isoproterenol infusion rate; these changes disappeared as the infusion rate was increased. The present study suggests intrinsic cardiac changes are present in this family with Romano-Ward syndrome. Their relationship to any extrinsic sympathetic defect is unclear. © 1978.