A review of heart rate and blood pressure responses in the cold in healthy subjects and coronary artery disease patients.

Despite methodological differences in the limited number of studies reviewed, it appears that cardiovascular responses at rest and during exercise in the cold differ between patients with CAD and healthy subjects (Figures 1 and 2). This difference remains, even when attempting to control for investigation time and conditions. Typical exercise time reported for patients with CAD exercising in the cold is 4 to 8 minutes, where HR and SBP are generally the same or higher. Data corresponding to a similar time frame (5-15 minutes) in healthy subjects show HR to be lower or no different, whereas SBP was similar in both studies. Logically, healthy subject's RPP values would be similar or lower in the cold, which may be a teleological development to conserve myocardial oxygen uptake in the face of elevated sympathetic stimulation during cold exposure. The lower HR would offset the cold-induced hypertension and also help to preserve cardiac output. In healthy subjects, cardiac output is similar in the cold despite a higher stroke volume (SV) due to the lower HR. However, the similar cardiac output reported by Epstein and colleagues in patients with CAD, both at rest and during exercise at 15 degrees C, was obtained by increases in SV and HR. A blunted peripheral vasoconstriction response in older subjects could lead to reduced central blood volume with a corresponding decrease in venous return and SV. An inability to maintain an appropriate SV in the cold by patients with CAD may be responsible for the elevated HR to maintain cardiac output. However, in healthy subjects, SV appears to have a triphasic response.(ABSTRACT TRUNCATED AT 250 WORDS)