The superfast atrial recharge pulse: a cause of pectoral muscle stimulation in patients equipped with a unipolar DDD pacemaker.

Pectoral muscle stimulation may cause serious discomfort to patients equipped with a pulse generator. Insulation defects of the lead, connector problems and defective coating of the pacemaker can are common causes of local muscle contractions. This report describes pectoral muscle stimulation caused by the atrial superfast recharge pulse incorporated into the atrial channel of a commercially available unipolar DDD pacemaker. As pectoral muscle stimulation could not be eliminated by reprogramming the pacemaker to a lower atrial output in some patients a redesign of the pacemaker is highly required.

Effects of intravenous sotalol, aprindine and the combination of sotalol and aprindine on chronic high frequency ventricular arrhythmias in man.

The comparative antiarrhythmic efficacy of three different intravenous drug regimens was evaluated in 12 symptomatic patients (mean age: 72 years) with chronic high frequency ventricular arrhythmias (mean: 834 PVCs h-1). In a cross-over study with latin square distribution the following drug regimens were administered intravenously to all patients aprindine 2 mg kg-1, sotalol 1.5 mg kg-1, aprindine 1 mg kg-1 & sotalol 0.75 mg kg-1. The mean percentage of PVC reduction was 41% (P less than 0.05) for aprindine 2 mg kg-1; 51% (P less than 0.05) for sotalol 1.5 mg kg-1 and 72% (P less than 0.01) for the combined drug therapy (aprindine 1 mg kg-1 and sotalol 0.75 mg kg-1). The mean plasma concentration was 1371 ng ml-1 after administration of aprindine 2 mg kg-1 and 1730 ng ml-1 after infusion of sotalol 1.5 mg kg-1. After combined drug therapy, mean plasma levels were 942 ng ml-1 for aprindine and 992 ng ml-1 for sotalol. The different drug regimens were well tolerated in all patients and no side-effects occurred. Combination therapy consisting of a drug that prolongs action potential duration with an antiarrhythmic agent that has a high affinity for the inactivated channels may thus achieve an antiarrhythmic efficacy comparable to single agent therapy, permitting the use of lower dosages.

Prediction of Wenckebach behavior and block response in DDD pacemakers.

At higher atrial rates, the behavior of a DDD pulse generator will depend on the atrial rate or spontaneous atrial interval (SAI) and the settings of the pacemaker: upper rate interval (URI), atrioventricular interval (AVI), and atrial refractory interval (ARI). An algorithm was developed enabling the prediction of the degree of Wenckebach block using the parameters mentioned above. In the absence of the programmed settings of the pacemaker, these parameters can be determined by noninvasive methods. AVI can be measured by application of a magnet over the pulse generator, while URI and ARI can be estimated during chest wall stimulation by progressively increasing the frequency of the external extrastimuli. The use of the formula in combination with chest wall stimulation allows the evaluation of the proper functioning of any DDD pacemaker during exercise and in patients with atrial rhythm disturbances, even when no information about the pacemaker settings is available.

Catheter technique for electrical ablation of the atrioventricular conduction system.

Seven patients with recurrent supraventricular arrhythmias, resistant to conventional drug therapy, were treated with electrical ablation of the atrioventricular (AV) conduction system. Permanent AV block was produced in five patients. Restoration of AV conduction occurred in two patients. The procedure of electrical ablation was well tolerated, without complications.

Emergency bypass surgery: late effects on size of infarction and ventricular function.

Using thallium myocardial scintigraphy and radionuclide ventriculography, we assessed size of infarction and left ventricular function at late follow-up (greater than 2 months) in 13 patients who underwent emergency coronary artery bypass surgery (ECABS) during evolving myocardial infarction and in 26 controls who received conventional treatment for acute infarction. Thallium scans were quantitatively analyzed. The thallium defect, expressed as a numerical value in arbitrary units, was smaller after early revascularization (within 4 hr of the onset of symptoms, n = 10) than in the controls: 397 +/- 232 vs 2779 +/- 972 for anterior infarction (p less than .001) and 475 +/- 511 vs 1454 +/- 960 for inferior infarction (p less than .05). The patients undergoing revascularization late (4 to 5 hr after the onset of symptoms, n = 3) had thallium defects comparable to those in the controls. Regional ejection fraction of the involved left ventricular segment was higher after early revascularization (41 +/- 9% vs 21 +/- 8% for anterior infarction, p less than .005; 67 +/- 14% vs 51 +/- 11% for inferior infarction, p less than .01). Global ejection fraction was higher after early revascularization in patients with anterior infarction (57 +/- 10% vs 37 +/- 9%, p less than 0.02), but not in those with inferior infarction (60 +/- 11% vs 54 +/- 8%, p greater than .05). After late revascularization, regional and global ejection fraction were comparable to those in controls. In selected patients, early reperfusion of acutely ischemic myocardium by ECABS can limit size of infarction and preserve left ventricular function, but time constraints may be severe.

Coronary artery surgery in patients with myxoedema.

Thyroid replacement therapy in patients with myxoedema associated with coronary atherosclerosis often exacerbates angina or occasionally precipitates myocardial infarction. Coronary revascularization has been proposed for these patients. In an attempt to evaluate the risks of anesthesia and surgery in hypothyroidism against the possible occurrence of a coronary event during preoperative thyroid replacement therapy, we reviewed the literature and report an additional five hypothyroid patients undergoing coronary bypass grafting without operative complications. It seems recommendable not delay thyroid replacement therapy in hypothyroid patients, who need coronary artery surgery, until a few days after the intervention.