[Respiratory insufficiency and cardiac arrhythmia: the rationale of treatment]

It is well known that the incidence of cardiac arrhythmia is particularly high in patients with chronic respiratory insufficiency (CRI). This study examines the prevalence, incidence and prognostic clinical importance of arrhythmia occurring during the course of CRI on the basis of data taken from the literature and the authors' personal experience using dynamic electrocardiographic diagnosis (24-hour Holter monitoring). The majority of arrhythmias observed in these patients appeared to take the form of premature ventricular and/or supraventricular beats and less frequently of atrial fibrillation and/or attacks of supraventricular paroxysmal tachycardia. Cardiac rhythm alterations were observed using Holter monitoring in 70-90% of patients. No cardiac rhythm disorder is specific to this pathological condition. The aim of this study was to formulate, as far as was possible, a rational therapeutic approach which took account of the electrogenesis of arrhythmic phenomena, variations in the type of arrhythmia and the hemodynamic conditions under which they occur. The etiopathogenesis of arrhythmias within the framework of CRI is relatively complex and probably multifactorial since there are a number of concomitant pathological conditions able to trigger off arrhythmogenic processes both inducing the onset of reflux circuits and enhancing cardiac automatism centres. Many studies correlate the presence of arrhythmia with hypoxemia, hypercapnia and both respiratory and metabolic alkalosis. Even the combined effect of hypoxia with respiratory acidosis and the integrity or otherwise of cardiac function (chronic pulmonary heart, right ventricular hypertrophy, ischemic cardiopathy) have a notable pro-arrhythmic effect. Hypokalemia induced by both respiratory alkalosis and by drugs used during the course of CRI (eg diuretics and/or steroids) may induce a marked dispersion of refractory periods of the various fibrocells thus encouraging the onset of arrhythmia. With regard to drugs, it has been observed that both digitalis and theophylline and beta-2 stimulants if frequently used during the course of CRI may possibly induce arrhythmia. It is therefore important to underline that they should be used with particular caution. As far as concerns the use of beta-2 adrenergic compounds, it is advised that they be administered using an aerosol rather than systemic route. Digitalis has limited indications; the molecules of the methylxanthine classes require careful pharmacological dose monitoring. Arrhythmic therapy should also be seen in terms of prophylaxis and the correction of predisposing and decisive factors such as hypoxemia, hypercapnia, hemoglobin and electrolyte levels, and alterations in blood pH following the obstruction of small airways.(ABSTRACT TRUNCATED AT 400 WORDS)