The risk of pacing after infarction, and current recommendations

Cost-effectiveness analysis in heart disease, Part III: Ischemia, congestive heart failure, and arrhythmias

Cost-effectiveness analyses were reviewed in the following diagnostic and treatment categories: acute myocardial infarction (MI) and diagnostic strategies for coronary artery disease (CAD), coronary artery bypass graft (CABG) surgery, percutaneous transluminal coronary angioplasty (PTCA), congestive heart failure (CHF), and arrhythmias. In the case of acute MI, coronary care units, as presently used, are rather expensive but could be made much more efficient with more effective triage and resource utilization; reperfusion via thrombolysis is cost-effective, as are beta-blockers and angiotensin-converting enzyme (ACE) inhibitors post-MI in appropriate patients. Cost-effectiveness of CAD screening tests depends strongly on the prevalence of disease in the population studied. Cost-effectiveness of CABG surgery depends on targeting; eg, it is highly effective for such conditions as left-main and three-vessel disease but not for lesser disease. PTCA appears to be cost-effective in situations where there is clinical consensus for its use, eg, severe ischemia and one-vessel disease, but requires further analysis based on randomized data; coronary stents also appear to be cost-effective. In preliminary analysis, ACE inhibition for CHF dominates, ie, saves both money and lives. Cardiac transplant appears to be cost-effective but requires further study. For arrhythmias, implantable cardioverter defibrillators are cost-effective, especially the transvenous device, in life-threatening situations; radiofrequency ablation is also cost-effective in patients with Wolff-Parkinson-White syndrome apart from asymptomatic individuals; and pacemakers have not been analyzed except in the case of biofascicular block, where results were variable depending on the situation and preceding tests.

Prognostic significance of complete atrioventricular block in patients with acute inferior myocardial infarction with and without right ventricular involvement

Data were obtained and analyzed in 243 patients with acute inferior myocardial infarction who were admitted to the coronary care unit during the years 1987 and 1988. One hundred and ninety-eight patients had no signs of right ventricular involvement (group I), whereas 45 patients had inferior myocardial infarction with right ventricular infarction (group II). Patients were divided into groups depending on the presence or absence of complete atrioventricular block during hospital stay (groups Ia and IIa without block and groups Ib and IIb with block). Selected clinical and laboratory variables were compared for each group. We found that patients with inferior myocardial infarction and complete atrioventricular block had significantly higher mortality rates only in the presence of right ventricular infarction: 41% mortality rate in group IIb versus 11% mortality rate in group Ib (p less than 0.05). Patients with right ventricular infarction but without complete atrioventricular block (group IIa) had a mortality rate similar to that found in patients with inferior myocardial infarction and no atrioventricular block (group Ia): 14% versus 11% (p = NS). In patients with inferior myocardial infarction without right ventricular involvement (group I), complete atrioventricular block did not influence survival: 14% mortality rate in group Ib versus 11% mortality rate in group Ia (p = NS). The excessively high mortality rate in patients who have inferior myocardial infarction with right ventricular involvement and complete atrioventricular block could be the consequence of greater infarct size, but the synergistic influence of right ventricular infarction and complete atrioventricular block could be the other factor that influences outcome.

Long-term outcome in patients with inferior myocardial infarction and complete atrioventricular block

Some studies have reported increased short-term mortality and higher incidence of multivessel coronary artery disease in patients with inferior myocardial infarction and complete heart block, but information is lacking on clinical outcome after hospital discharge. Therefore, data were obtained and analyzed in 749 patients who were admitted with inferior myocardial infarction to four different centers and followed up for 1 year. Six hundred fifty-four patients (Group 1) did not have complete heart block and 95 (Group 2) had complete heart block during their hospital stay (incidence rate 12.8%). Compared with Group 1, Group 2 patients were older (66 versus 61 years, p less than 0.01), more often had signs of left ventricular failure (p less than 0.001) and had higher peak creatine kinase values (1,840 versus 1,322 IU/liter, p less than 0.001). The in-hospital mortality rate was higher in Group 2 than in Group 1 (24.2 versus 6.3%, p less than 0.001). However, at discharge there was no difference between Group 1 and Group 2 in clinical characteristics, left ventricular ejection fraction (0.52 +/- 0.12 versus 0.52 +/- 0.11) or incidence of complex ventricular arrhythmias on ambulatory electrocardiographic monitoring. Furthermore, during the year after hospital discharge, patients in Groups 1 and 2 did not have significantly different mortality rates (6.4 versus 10.1%, p = NS). The incidence rate of reinfarction (4%) was the same in Groups 1 and 2. The incidence of coronary artery bypass surgery was slightly but not significantly higher in Group 1 compared with Group 2 (11 versus 4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic monitoring and pacing with one catheter: a pilot study

Attempts to incorporate the monitoring of central pressures and pacing into one catheter have heretofore been unsuccessful. Recently, a new catheter for monitoring central hemodynamic pressures, which has a right ventricular port (Chandler pacing port), has been devised, which has been reported to allow for simultaneous acquisition of hemodynamic data and reliable pacemaker function as well. To assess the reliability of this catheter, we studied ten consecutive Swan-Ganz catheterizations utilizing this new catheter system. In all instances, hemodynamic monitoring was established without difficulty. In three instances, because of right heart enlargement, fluoroscopy was necessary to position the pacing probe at the right ventricular apex. In all ten instances, a threshold of less than 2.5 mV was obtained. Isolated PVCs and nonsustained ventricular tachycardia were common during insertion. After initial placement, the threshold for sensing and pacing was assessed every 6 hr. Malfunction occurred in three patients. In all, repositioning was accomplished without marked difficulty; in one it required fluoroscopy. In three instances, the Swan-Ganz pacing catheter system malfunctioned. These data are similar to data utilizing other modalities of temporary pacing and suggest that this catheter may be capable of providing hemodynamic monitoring and pacing from a single percutaneous procedure.

The Birmingham Trial of permanent pacing in patients with intraventricular conduction disorders after acute myocardial infarction

Patients surviving 2 weeks after myocardial infarction who had persistent conduction disorder (right bundle branch block alone or associated with left anterior or posterior hemiblock [LPH] or LPH alone) were allocated at random to permanent pacing or control groups. Throughout follow-up, up to 5 years, there was no significant difference in survival: at 2 years 14 of 23 (61%) of paced patients had died compared with 11 of 27 (41%) control patients. Progression of conduction disorder was not observed and measurement of infranodal conduction time (HV interval) did not predict outcome. Ventricular tachyarrhythmias were an important cause of death in these patients and pacing appears to offer no benefit.

Care of patients with a low probability of acute myocardial infarction. Cost effectiveness of alternatives to coronary-care-unit admission

We conducted a cost-effectiveness analysis to examine the clinical and economic consequences of alternatives to admission to a coronary-care unit for patients who have a relatively low probability of acute myocardial infarction. Despite the fact that all our assumptions were slanted to favor the current standard policy of admission to a coronary-care unit, our analysis shows that admission to an intermediate-care unit providing resuscitative facilities and prophylactic lidocaine is highly cost effective. For patients with about a 5 per cent probability of infarction, admission to a coronary-care unit would cost $2.04 million per life saved and $139,000 per year of life saved, as compared with intermediate care. For the expected number of such patients annually in the United States, the cost would be $297 million to save 145 lives. At probabilities of infarction up to about 20 per cent, the incremental cost to save a year of life by choosing a coronary-care unit over an intermediate-care unit would be higher than the estimated cost of saving a year of life by treating a 40-year-old man with mild hypertension. Our results suggest that many patients who have a low risk of acute myocardial infarction would be appropriate candidates for admission to an intermediate-care unit.

Prevention of myopotential inhibition of unipolar QRS-inhibited demand pacemakers

Seventy-two unipolar QRS-inhibited demand pacemakers were examined by provoking myopotential interference by exercise. Filter characteristics of 5 kinds of generators were tested by the use of sin wave pulse. Each myosignal of the major pectoral muscle and the abdominal rectus muscle was subjected to Fourier transform for analyses of amplitude and frequencies. Pacemaker inhibition was observed in 42 (58 per cent) of 72 with the highest frequency in the push up test. In this test, the incidence of myopotential inhibition was significantly lower (p less than 0.01) on the pacemaker implantations in the abdominal wall than that in the anterior chest wall. The myosignals of the major pectoral muscle had sufficient frequency and power density for triggering the QRS sensing mechanism but the abdominal muscular signals did not. To avoid myopotential inhibition of unipolar ventricular inhibited demand pacemakers it is most effective to implant multiprogrammable pacemakers subcutaneously in the abdominal wall and to select the optimal sensitivity according to the myopotential inhibition tests.

Myopotential inhibition of unipolar AV sequential (DVI) pacemaker

Whereas myopotential inhibition of QRS-inhibited (VVI) pacemakers is well known, its occurrence in patients with AV sequential (DVI) pacemakers has not been reported. The present communication deals with spontaneous and induced myopotential inhibition of a multiprogrammable Intermedics unipolar AV sequential (DVI) pacemaker. The bedside maneuvers that were performed in the patient exposed the problem, therefore serving to establish the diagnosis. Although external adjustment of the sensitivity was the simple, non-invasive solution in this case, more studies are required to determine the success rate of this approach as well as the incidence and clinical significance of myopotential inhibition of unipolar DVI pacemakers.

Ventricular fibrillation complicating pacemaker insertion in acute myocardial infarction

Temporary transvenous pacing catheters were placed in 101 patients with acute myocardial infarction (MI) for the management of bradyarrhythmias or conduction disturbances. Fourteen (14%) patients (group A) developed ventricular fibrillation (VF) at the time of pacing catheter manipulation in the right ventricle. Compared to the remaining 87 (86%) patients (group B), the patients in group A were younger (56.1 vs 65.8 yrs, P = 0.007). Thirteen (92.8%) of 14 patients in group A had inferior MI compared to 58 (66.6%) of 87 patients in group B (P = 0.04). All but one patient in group A had pacemaker insertion within 24 h of the onset of symptoms of MI compared to 55 (63%) of 87 in group B (P = 0.02). In 12 of the 14 patients in group A, following defibrillation and intravenous bolus administration of lidocaine, the pacing catheter was positioned in the right ventricle without further episodes of VF. It is concluded that 1) in patients with acute MI temporary transvenous pacemaker insertion may be complicated by VF; 2) VF is most likely to occur in younger patients with inferior MI infarction when the pacing catheter is inserted within 24 h of the onset of symptoms of infarction; and 3) administration of an intravenous bolus of lidocaine may be effective in preventing the induction of VF by catheter manipulation.

Ventricular fibrillation complicating temporary ventricular pacing in acute myocardial infarction: significance of right ventricular infarction

Five patients with acute myocardial infarction had ventricular fibrillation as a complication of indicated temporary pacing. All five patients had evidence of right ventricular infarction (three patients with postmortem confirmation). The presence of right ventricular infarction seems to be a contributing mechanism involved in the induction of ventricular fibrillation during temporary pacing for bradyarrhythmia complicating acute myocardial infarction.

Undersensing of demand pacemakers in acute myocardial infarction

Trasient asynchronous pacing due to abnormal sensing function is reported in two patients with inserted demand pacemakers during the early phase of acute myocardial infarction. The hazards of the pacemaker induced parasystole with R on T phenomenon in conditions of enhanced electrical instability could be successfully overcome applying overdrive suppression of the inserted pacing system by external chest wall stimulation.

Myopotential inhibition of unipolar QRS-inhibited (VVI) pacemakers, assessed by ambulatory Holter monitoring of the electrocardiogram

Seventy-four patients with unipolar QRS-inhibited pacemakers (VVI) were Holter monitored to assess the occurrence of pacemaker inhibition caused by skeletal muscle potentials during daily activities. Fifty patients had high-grade atrioventricular block and 24 had sinoatrial disease. Chest wall stimulation prior to monitoring revealed asystole of > 4 seconds duration in 22 patients, and ventricular rates between 25 and 56 beats per minute in 52 patients. Fifty-one patients (69%) had one or more episodes of pacemaker inhibition from myopotentials. Inhibition occurred in all types of pacemakers studies, but was most frequent and of longest duration in patients with Siemens-Elema 207/70 (13/14 patients), Cordis Omni-Stanicor (6/7 patients), CPI Microlith (5/6 patients), and Medtronic 5945 (8/10 patients). This was not unexpected considering the filter characteristics of the pacemakers. Nine patients (12%) presented symptoms which might be ascribed to pacemaker inhibition. The longest asystole observed was 3.2 s. Seven patients had pacemakers spikes falling on or near T-waves of spontaneous heart beats because their pacemakers had been rendered refractory by myopotentials. No serious arrhythmias were seen during episodes of pacemaker inhibition or interference. More emphasis should be put on the improvement of filter characteristics of unipolar VVI-pacemakers. Pacemaker patients with symptoms of myopotential inhibition should be equipped with either a bipolar or ventricular triggered (VVT) pacemaker or with a sensitivity and/or pacing mode programmable pacemaker.

Risks of delayed potentials in pacemaker patients prone to ventricular tachycardia

Late potentials occurring after completion of the QRS complex have been observed in patients prone to ventricular tachycardia. They were recorded either during epicardial studies or in the catheterization laboratory. This paper describes such abnormal myocardial activity and discusses their potential effects on cardiac pacemakers.

Successful treatment of myocardial perforation and tamponade after temporary endocardial pacing

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Long-term prognosis after acute anterior infarction with atrioventricular block

The purpose of this study was to evaluate the need for permanent pacing in patients who have survived the effects of anterior myocardial infarction with complete heart block and have returned to sinus rhythm but who are left with impairment of intraventricular conduction. We have reviewed 52 patients with complete heart block complicating recent anterior myocardial infarction. Temporary pacing was instituted in all patients. There were 25 hospital survivors who were followed for an average of 49 months. Long-term pacing was established in 4 patients. Of the 21 patients in sinus rhythm, 14 had partial bilateral bundle-branch block with either right bundle-branch block and left anterior hemiblock or right bundle-branch block and left posterior hemiblock; at the end of the follow-up period, 10 of these 14 were alive and well. Furthermore, permanent pacing failed to prevent sudden death in 2 patients. At the present time, therefore, we conclude that long-term pacing is not justified in patients, otherwise asymptomatic, with partial bilateral bundle-branch block persisting after transient complete heart block in anterior myocardial infarction.

Heart block complicating acute inferior wall myocardial infarction

Heart block was noted in 60 (35 complete and 25 second-degree) of 410 patients with acute inferior wall myocardial infarction. This group with heart block was compared to a control group of 30 patients with acute inferior wall infarction without heart block. The incidences of prior myocardial infarction and hypertension, in addition to the highest level of serum creatine phosphokinase and a maximum degree of ST-segment elevation in the inferior leads, were all greater in patients with heart block, as compared to the controls. The incidences of various complications, including dizziness and syncope, transient hypotension, cardiogenic shock, and congestive heart failure, were also higher in the group with heart block, while sinus nodal distrubances and atrial arrhythmias occurred with equal frequency. The mortality in those with heart block was 28 percent compared to 13 percent for the control. It is concluded that patients with heart block complicating acute inferior myocardial infarction have a greater amount of myocardial necrosis, a higher incidence of complications, and a higher mortality. Insertion of a temporary pacemaker should be considered when specific indications are present and not routinely.

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.

Implanted-pacemaker-induced dysrhythmia and its management

Five cases of implanted-pacemaker-induced dysrhythmia are described and factors precipitating such dysrhythmias are discussed.

The efficacy of practolol in the treatment of such dysrhythmias is shown and its use as a prophylactic antidysrhythmic agent has been suggested.

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.

Peritoneal dialysis for pulmonary oedema after acute myocardial infarction

Four patients with intractable pulmonary oedema after acute myocardial infarction were treated with peritoneal dialysis. A negative fluid balance was rapidly achieved in three patients, two of whom ultimately survived. The fourth patient, who had complete heart block at the beginning of dialysis, showed initial clinical improvement with restoration of sinus rhythm despite failure to extract fluid.