Artificial pacing by electrode catheter for heart block or asystole complicating acute myocardial infarction

Treatment of the bradycardia-tachycardia syndrome with permanent demand pacing

The bradycardia-tachycardia syndrome (paroxysmal supraventricular tachycardia alternating with sinus bradycardia and episodes of sinus node arrest) has previously presented a complicated therapeutic dilemma when excitatory and suppressive drugs have been utilized. A patient with this syndrome successfully treated with a permanent ventricular transvenous demand pacemaker is presented. Various aspects of this syndrome as well as facets of diagnosis and treatment have been reviewed and discussed. Significant underlying cardiac disease was ruled out in this patient by the usual diagnostic methods including left heart catheterization and coronary angiography. An interesting possibility of the relationship of vagal stimulation secondary to hiatus hernia as an etiologic factor in this syndrome has been discussed. The opinion is expressed that the currently preferred method of treatment is the insertion of a permanent transvenous pacemaker alone or in conjunction with antiarrhythmic drugs, preferably digitalis and propranolol.

Significance of high degree atrioventricular block in acute posterior myocardial infarction. The importance of clinical setting and mechanism of block

This report evaluates the morbidity and mortality, during hospitalization and follow-up, of a subgroup of patients with posterior or diaphragmatic myocardial infarction (PDMI) who developed high degree A-V block via a type I mechanism and in the absence of power failure (pulmonary edema or cardiogenic shock). This subgroup was not at any higher risk of hospital morbidity, hospital mortality, or 1-year mortality than three other groups: (a) patients with PDMI but neither high degree A-V block nor initial power failure; (b) patients with other infarct sites who developed high degree A-V block in the absence of power failure; and (c) patients with other infarct sites but neither high degree A-V block nor initial power failure. The significance of subgrouping patients with high degree A-V block by the quantity of clinical heart failure is exemplified by a review of the literature and the present study.

Atrioventricular and associated intraventricular conduction disturbances in acute myocardial infarction

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Experiences of coronary intensive care in a district hospital

Seven hundred and twenty-one patients were admitted during 22 months. Recent myocardial infarction was confirmed in 518. In this group, 115 (22%) died in hospital and 33 (6%) were resuscitated and left hospital alive. Prophylactic measures probably prevented cardiac arrest in a number of patients and contributed to lowering the mortality rate. Other factors influencing cardiac arrest and death were sex, age, time after onset of infarction and ECG pattern. Anticoagulants had no influence. The clinical presentation was most varied and several difficult diagnostic patterns are described.

Pacing after acute myocardial infarction

Experience of endocardial pacing in eighty-two patients with atrioventricular block after myocardial infarction is described. A unipolar pacing wire was passed into an antecubital fossa vein and passed into the right atrium and wedged into the apex of the right ventricle under radiological control using an image intensifier. All patients were attached to an external demand unit set at 60/min which will pace if there is asystole longer than 1 sec. The disadvantages of pacing are discussed.

A fall in mortality occurred from 71% of unpaced patients to 38% of thirty-seven patients where demand pacing was given. When suppressant drugs (lignocaine, procainamide and quinidine) were given in addition to pacing the mortality dropped to 11% of twenty-seven patients. The disadvantages of pacing are few and it is considered that suppressant drugs are only used with safety when a pacing system has been installed.

Transvenous cardiac pacing. Experience of a percutaneous supraclavicular approach

A detailed description is given of a technique for the introduction of cardiac pacing catheters using a percutaneous supraclavicular route through the subclavian vein. In 91 attempts there was only one failure and the frequency of complications was low. Surface landmarks for the procedure were easy to define precisely, and stable pacing could usually be established rapidly without distress to the patient or subsequent immobilization of any limb. It is suggested that operators with little experience of cardiac catheterization might find this approach valuable in the emergency pacing of acute heart block. Subclavian venepuncture does not appear to be as hazardous as has previously been suggested.

Myocardial infarction and complete heart block

The clinical and electrocardiographic records of 20 patients with complete A-V block due to acute myocardial infarction have been analyzed. This study indicated that patients with an inferior wall myocardial infarction had, most commonly, a block above the bifurcation. The block was transitory, the patients had no Stokes-Adams attacks and the outcome was good. None of our patients required artificial pacing. On the other hand, patients with an anteroseptal myocardial infarction suffered from a bilateral bundle branch block (below the bifurcation). They had severe Stokes-Adams attacks and they all required artificial pacing. The destruction of the conducting system was extensive and the outcome was poor. Five out of seven patients treated with artificial pacing recovered the A-V conduction through the left bundle within a few days. However, in spite of this they all died.From this small series clearly defined clinical and electrocardiographic features can be identified in two different groups of cases.

Bundle-branch block in acute myocardial infarction

Bundle-branch block was present in 41 out of 415 patients admitted to a coronary care unit with acute myocardial infarction and was associated with more severe clinical infarction and an overall mortality of 56%. It is probable that permanent bundle-branch block develops soon after infarction and that most of the patients with permanent block have had clinically severe infarction. Bundle-branch block developing during observation is usually transient, and the later it develops the sooner it resolves.Analysis of the arrhythmias and clinical course of the patients suggests that those with bundle-branch block and shock and those in whom bundle-branch block is present on admission may benefit from the use of a demand pacemaker attached to a transvenous pacemaker catheter, though the dividends of pacing may be small and the risks of the procedure significant. Post-mortem examination of 17 hearts showed extensive infarction, usually involving the septum, and severe coronary artery disease.

Hemodynamic effects of artificial pacing in complete heart block complicating acute myocardial infarction

The hemodynamic changes associated with complete heart block complicating acute myocardial infarction and the effects of artificial pacing at various rates on these measurements were studied in 13 patients. Studies were performed on the first day of complete block in all patients and were repeated on subsequent days in six.

With two exceptions cardiac output was increased by pacing. In patients paced at progressively increasing ventricular rates, the rate associated with the maximal cardiac output exceeded 100/min, with one exception. However, an adequate response usually occurred between 80 and 90/min. Stroke volume fell as the rate was increased with pacing in most patients, but rose in some, suggesting improved myocardial performance. Systemic blood pressure increased, and the change paralleled cardiac output changes fairly closely as pacing rates were increased. The blood pressure did not, however, reflect reliably the absolute level of cardiac output either in heart block or after the return of sinus rhythm. Systemic vascular resistance was high in most patients with low cardiac outputs and fell with pacing at maximal output rates. There was no consistent change in mean right atrial or mean pulmonary arterial pressure with pacing during the period of study. Tension time index was low in heart block, and increased considerably with pacing, implying a corresponding increase in myocardial oxygen requirements.

Pacing improved signs of depressed mental function and poor skin circulation which were invariably associated with a severe reduction in cardiac output. These signs were found to be superior to heart rate and blood pressure in clinical evaluation of the adequacy of the cardiac output in heart block and the response to pacing.