Mechanisms of arrhythmias in chronic obstructive lung disease.

Because of the close anatomic and physiologic relationship between the heart and lungs, patients with chronic obstructive lung disease are at special risk of arrhythmias. Effective therapy hinges on identifying the mechanisms of the arrhythmias--hemodynamic, metabolic, or drug-induced. Impulsive use of antiarrhythmic agents may result only in a more complex and dangerous rhythm disorder. Extremes of pH are a major cause of arrhythmias in these patients. Respiratory alkalemia usually originates with inappropriate ventilation, often during mechanical respiration, while metabolic alkalemia generally can be traced to diuretic or bicarbonate therapy. Lidocaine or diphenylhydantoin are of little use, since the alkaline pH inside and outside heart muscle cells hampers drug distribution and activity. At the other extreme, the arrhythmias of acidemia strike patients who have severe respiratory failure with carbon dioxide retention or severe cardiac failure with shock and lactic acidemia. Arrhythmias may develop if vagal restraint is lost, which is especially likely in patients with potassium depletion. Irritant receptors along the bronchopulmonary tree can trigger arrhythmias if stimulated by cough, microembolism, or mechanical irritation, which is a hazard with endotracheal or tracheostomy tubes.