The purpose of this echocardiography study was to measure peak coronary blood flow velocity (CBV peak) and left ventricular function (via tissue Doppler imaging) during separate and combined bouts of cold air inhalation (-14 ± 3°C) and isometric handgrip (30% maximum voluntary contraction). Thirteen young adults and thirteen older adults volunteered to participate in this study and underwent echocardiographic examination in the left lateral position. Cold air inhalation was 5 min in duration, and isometric handgrip (grip protocol) was 2 min in duration; a combined stimulus (cold + grip protocol) and a cold pressor test (hand in 1°C water) were also performed. Heart rate, blood pressure, O 2 saturation, and inspired air temperature were monitored on a beat-by-beat basis. The rate-pressure product (RPP) was used as an index of myocardial O 2 demand, and CBV peak was used as an index of myocardial O 2 supply. The RPP response to the grip protocol was significantly blunted in older subjects (Δ1,964 ± 396 beats·min -1·mmHg) compared with young subjects (Δ3,898 ± 452 beats·min -1·mmHg), and the change in CBV peak was also blunted (Δ6.3 ± 1.2 vs. 11.2 ± 2.0 cm/s). Paired t-tests showed that older subjects had a greater change in the RPP during the cold + grip protocol [Δ2,697 ± 391 beats·min -1·mmHg compared with the grip protocol alone (Δ2,115 ± 375 beats·min -1·mmHg)]. An accentuated RPP response to the cold + grip protocol (compared with the grip protocol alone) without a concomitant increase in CBV peak may suggest a dissociation between the O 2 supply and demand in the coronary circulation. In conclusion, older adults have blunted coronary blood flow responses to isometric exercise.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|State||Published - Apr 15 2012|
All Science Journal Classification (ASJC) codes
- Cardiology and Cardiovascular Medicine
- Physiology (medical)