Effect of hypoxaemia on the resting electrocardiogram (ECG) in patients with cardiac ischaemia.
The effect of hypoxaemia on the heart at rest was studied using the electrocardiogram (ECG) in 38 patients. The majority had symptoms of cardiac disease and all were scheduled to have an exercise ECG test under standard conditions. Two ECG variables were examined; (i) depression of the ST segment at the point 60 ms after the QRS-ST junction as well as (ii) the slope of the J-60 ms segment. During exercise breathing air, 11 patients showed positive changes of cardiac ischaemia, 5 were equivocal and 22 showed little or no change. When the patients had recovered from the exercise study they breathed a hypoxic mixture to lower their arterial oxygen saturation to 85% for 3 minutes. No changes were seen in the ST segment in any subject. We conclude that a 3-minute period of hypoxaemia at an oxygen saturation of 85% with subjects at rest did not cause ST segment depression in patients with either positive or negative exercise tests.
Princess Margaret Hospital, Swindon, UK.
M D
MD
Entwistle
D
D
Sommerville
A P
AP
Tandon
J G
JG
Jones
D000328:Adult; D000787:Angina Pectoris / Q000503:physiopathology; D004244:Dizziness / Q000503:physiopathology; D004417:Dyspnea / Q000503:physiopathology; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*; D009609:Nitrous Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D005082:Physical Exertion / Q000502:physiology; D012146:Rest / Q000502:physiology; D012815:Signal Processing, Computer-Assisted
D009609:Nitrous Oxide; D010100:Oxygen