HEART-RATE STROKE VOLUME RELATIONSHIP DURING UPRIGHT EXERCISE IN LONG-TERM DIABETICS

The changes in stroke volume (SV) during upright exercise were studied in 20 insulin-dependent diabetics (IDDM) and 20 age- and sex-matched controls. None of the diabetics had any cardiovascular symptoms. In ad dition, tests of autonomic function were conducted in the diabetics, a ssessing changes in heart rate (HR) during deep breathing and the Vals alva maneuver. During exercise the SV in the controls gradually increa sed and then remained essentially unchanged until maximum HR was achie ved. Seven of the diabetics failed to sustain an initial increase in S V (fall > 15%), eight showed a ''delayed'' increase in SV, and the rem aining five demonstrated an increasing SV over the range from rest to peak exercise. Abnormal autonomic function results were found during d eep breathing (four diabetics) and the Valsalva maneuver (four diabeti cs). Findings indicate that cardiac function could be abnormal in IDDM without evidence of autonomic dysfunction. This abnormality could be due to a specific cardiomyopathy.