The effects of hypocapnia on cardiac electrical activity and heart function and its relevance to the diagnosis of coronary artery disease
Sheppard JP.
Current methods used in the diagnosis of coronary artery disease vary in sensitivity and specificity and have a number of limitations. The aim of this thesis investigation was to explore a new technique for inducing hypocapnia in resting subjects and investigate whether this technique has any clinical applications in the diagnosis of coronary artery disease. In 18 healthy subjects, the effects of hypocapnia, induced by mechanical hyperventilation (in 21% or 15% inspired O\(_2\)), on cardiac electrical activity and heart function were investigated using an electrocardiogram (ECG) and echocardiogram. In addition, a pilot study was conducted to examine the effect of hypocapnia on the ECG of four patients suffering from coronary artery disease with stable angina. Experiments using mechanical hyperventilation showed that the most severe hypocapnia tolerable (PetCO\(_2\) = 20 ± 0mmHg) in normal healthy subjects causes a significant increase in T wave amplitude (increase of up to 0.09 ± 0.02mV, P < 0.01) in the anteroseptal leads (V\({_1-3}\)) of 18 normal subjects but these changes do not exceed the clinical thresholds for hyperacute T wave amplitudes. Hypocapnia did not cause any other significant ECG or echocardiographic ... (continues)