Effects of a Reduction in Environmental Temperature on the Circulatory Response to Exercise in Man

The physiologic basis for the frequent complaint of worsening of symptoms in a cold environment was investigated in six patients with and five without coronary-artery disease, at rest and during identical levels of mild upright exercise at 25 and 15°C, with similar results. Significantly higher at the lower temperature were mean systemic arterial pressure (105 vs 92 mm of mercury at rest and 110 vs 92 during exercise; p less than 0.001), total peripheral resistance (1821 vs 1609 dynes-sec-cm-5 at rest, 1213 vs 993 during exercise; p less than 0.02) and left ventricular minute work (6.5 vs 5.7 kg-m at rest, 10.9 vs 9.0 during exercise; p less than 0.001). Exposure to cold did not change heart rate, cardiac output or stroke volume at rest or during exercise. These results indicate that a cold environment increases peripheral resistance at rest and during exercise. The consequent rise in arterial pressure, by augmenting myocardial oxygen requirements, would thus more readily provoke an attack of angina.