Disorders of the heart rhythm which consist basically of sinus bradicardia or sinus arrest correspond to a syndrome which has been named the sick sinus syndrome. Within the framework of this syndrome, there is a subgroup of alternating atrial bradycardia with episodes of atrial tachyarrhythmia. Generally known as the bradycardia-tachycardia syndrome, this subgroup is both electrophysiologically interesting and therapeutically challenging. This report is concerned with the experience obtained at the emergency ward and coronary care unit of the Instituto Nacional de Cardiología de México on the diagnosis and management of 8 patients with this syndrome. Various underlying heart conditions were present with predominance of ischemic heart disease. The clinical picture was dependent upon the hypoperfusion of vital organs secondary to the cardial arrhythmia. The most common symptoms were derived from cerebral circulatory deficit and coronary insufficiency. Half of the patients had moderate cardiac failure. All patients had spontaneous and transient loss of sinus function which lasted more than 2,000 msec. in seven. The bradycardia had a rate below 50 beats per minute in all cases except one. The tachyarrhythmias observed were atrial flutter, atrial fibrillation and paroxysmal supraventricular tachycardia. Three of the patients had more than one of these these tachyarrhythmias during the period of study. A discussion is made on the diagnosis of this syndrome by means of atrial pacing and interventions which modify either vagal or sympathetic tone. Considerations are also made on the frequent associated abnormality of the A-V functional tissues. Emphasis is placed on the problems encountered in the management of these patients. It is concluded that, in most cases, a satisfactory result may be obtained by the implantation of a permanent demand pacemaker associated to the administration of antiarrhythmic drugs.

Adult↗

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[Hemodynamic evaluation in acute myocardial infarct. Application to the treatment of contractile insufficiency syndromes of the left ventricle].

Even though the coronary care units have reduced to a minimum the mortality due to arrhythmias, the syndromes of left ventricular failure are responsible for the greatest part of hospital deaths in patients with acute myocardial infarction. The poor results depend upon the extensive destruction of left ventricular mass. The management in these cases should be directed to improve the performance of viable muscle as well as to preserve thejeopardized ischemic myocardium that is potentially viable. These goals may be adequately pursued by continuous hemodynamic characterization of left ventricular function. The experience of the Coronary Care Unit of the Instituto Nacional de Cardiología de México in the study of 30 of these patients is presented. Hemodynamic evaluations were performed by means of a Swan-Ganz catheter and cardiac output determinations by the thermodilution technique. The studies may be performed with a minimum of risk. Central venous pressure measurements do not adequately indicate the status of the left ventricle. Its function may be evaluated by the use of end diastolic pulmonary artery pressure which reflects, quite accurately, the left ventricular filling pressure in these patients. Continuous hemodynamic monitorization facilitates the proper manipulation of the determinants of ventricular performance (preload, afterload, cardiac rate and contractility) and permits an attempt to improve the balance between available oxygen and myocardial oxygen requirements. Hemodynamic studies and ventricular function curves are presented in selected patients with acute myocardial infarction. The mortality due to left ventricular failure and cardiogenic shock in patients with acute myocardial infarction remains extremely high. However, it is only through the early recognition by continuous hemodynamic monitorization and the aggressive management of the patient with incipient left ventricular failure that the number of survivors may be increased.

Female↗