The nonextractable tined endocardial pacemaker lead.

With the advent of the tined pacemaker electrode to improve endocardial fixation, increasing difficulty in extracting them when needed has resulted in reports of serious complications. The authors reviewed their experience between January 1975 and January 1985. During this 10 year period, 942 pacemakers were inserted and 73 were reoperated upon. In the reoperations, repositioning or removal of tined electrodes was attempted 28 times. Repositioning or removal was not possible in 12 of the 28 cases (43%). In 22 of 28, the attempts to remove tined leads were carried out more than one month after the original implantations and in this group the failure rate was 54.5% (12 of 22). All attempts of removal within one month of implantation were successful (six of six). No leads were retained during the period between January 1984 and January 1985. All 12 retained leads were followed-up for five years, five of which were retained in the presence of pacemaker pocket infections. After removal of the power pack and lead distal to the cephalic or subclavian vein inlet, control of infection was achieved in all five cases. One patient was noted to have the retained lead migrate into the right pulmonary artery but was asymptomatic at 35 months after catheter migration was detected. Until now, no thoracotomy for lead extraction has been required in this series.(ABSTRACT TRUNCATED AT 250 WORDS)

Beyond pure parasystole: promises and problems in modeling complex arrhythmias.

The dynamics of pure parasystole, a cardiac arrhythmia in which two competing pacemakers fire independently, have recently been fully characterized. This model is now extended in an attempt to account for the more complex dynamics occurring with modulated parasystole, in which there exists nonlinear interaction between the sinus node and the ectopic ventricular focus. Theoretical analysis of modulated parasystole reveals three types of dynamics: entrainment, quasiperiodicity, and chaos. Rhythms associated with quasiperiodicity obey a set of rules derived from pure parasystole. This model is applied to the interpretation of continuous electrocardiographic data sets from three patients with complicated patterns of ventricular ectopic activity. We describe several new statistical properties of these records, related to the number of intervening sinus beats between ectopic events, that are essential in characterizing the dynamics and testing mathematical models. Detailed comparison between data and theory in these cases show substantial areas of agreement as well as potentially important discrepancies. These findings have implications for understanding the dynamics of the heartbeat in normal and pathological conditions.

A prospective trial of new versus refurbished cardiac pacemakers: a Canadian experience.

Pacemaker reimplantation in the same patient is common, and pacemaker transplantation or reuse in a second patient has been reported. No report prospectively compares the long term costs, the impact of reuse on the number of pacemakers implanted, the pacemaker related complications, the types of patients selected and the patient survival of those who receive new versus a refurbished pacemaker. The authors implanted 70 pacemakers of which 75% (52) were new and 25% (18) were refurbished. The refurbished pacemakers were implanted in older patients (P less than 0.02), with a mean +/- SD of 77 +/- 8 versus 69 +/- 13 years of age. During a follow-up period of 36 months, the rate of pacemaker related complications was the same in both groups, with no unusual or unexpected problems arising in the refurbished group. There were 12 (23%) complications in the new pacemaker group and four (22%) complications in the refurbished pacemaker group. There were no major pacemaker related complications, no pacemaker battery depletions and no pacemaker related deaths. The refurbished pacemakers saved $33,000. After three years the cumulative probability of survival in the new group tended to be higher (P = 0.08) with a mean (SE) of 0.62 (0.12) versus 0.44 (0.15). New and refurbished pacemakers are similar with respect to pacemaker related survival and complications. Refurbished pacemakers effect a major reduction in pacemaker costs while maintaining health care standards.

Electrophysiologic effects of intravenous propafenone in Wolff-Parkinson-White syndrome.

The electrophysiologic effects of intravenous propafenone were studied in 15 consecutive patients with accessory pathways. Thirteen patients had sustained orthodromic supraventricular tachycardia induced during baseline study, and two patients needed isoproterenol to render it sustained. In all except one patient, propafenone, 2 mg/kg given intravenously over a 10-minute period, was successful in converting the arrhythmia to sinus rhythm. Atrial fibrillation was inducible in 10 patients before propafenone, but was no longer inducible in seven of these patients after the drug. The HV interval (23 +/- 20 to 41 +/- 25 msec) and the anterograde (310 +/- 96 to 509 +/- 145 msec) and retrograde (256 +/- 30 to 334 +/- 105 msec) effective refractory periods of the bypass tract were all significantly prolonged after the drug. The pacing cycle length that produced conduction block over the bypass tract anterogradely (319 +/- 126 to 446 +/- 150 msec) and retrogradely (272 +/- 25 to 360 +/- 97 msec) was also increased. During orthodromic tachycardia, propafenone increased conduction time in both the anterograde and retrograde limbs of the tachycardia. Tachycardia terminated in the retrograde limb in 64% of the patients. We conclude that propafenone is very effective in terminating orthodromic tachycardia when given intravenously and that it should be considered in patients initially seen with atrial fibrillation and short refractory periods.

Body surface isopotential mapping of permanent cardiac pacemaker spike amplitudes: a noninvasive method for detecting and localizing insulation failure.

Cardiac pacing systems produce cardiac contractions by delivering electrical charges to the myocardium. Reliable cardiac pacing, and the longevity of pacemakers depends on the absence of electrical leaks. Electrical leaks often do not cause symptoms and if suspected, there are few methods which are able to identify their location and none suited to small or intermittent leaks. We surface mapped the pacemaker spike amplitudes over the pockets of 29 patients with unipolar pacemakers, several of which had suspected pacemaker leaks. For each patient, pacer voltage spikes were recorded with an optical ECG recorder from sixty-three positions on the skin over the pacemaker. The spike voltages were interpolated with a 2-D Fourier transform, contoured, and plotted by a computer. Electrical leaks were readily detected and their positions indicated by the resulting maps. The operative findings confirmed the map guided prediction in all six patients sent for pacemaker revision. Pacemaker spike amplitude surface mapping detects and locates pacing system insulation failures.

Prediction of complex atrioventricular conduction rhythms in humans with use of the atrioventricular nodal recovery curve.

Theoretical considerations indicate that complex patterns of atrioventricular conduction produced by rapid atrial stimulation can be predicted from changes in atrioventricular conduction produced by premature stimulation of the atrium. The purpose of this study was to evaluate the validity of this theoretical approach in seven patients undergoing electrophysiologic investigation. The atrioventricular nodal recovery curve was determined at two different basic cycle lengths. Subsequently, periodic atrial stimulation was delivered for 30 sec periods over a range of frequencies giving 11, Wenckebach, reverse Wenckebach, and 21 rhythms. The recovery curve data was then used to compute the response to periodic stimulation by an iterative technique. The conduction patterns actually seen during periodic atrial stimulation showed close agreement with the computed patterns. This work thus provides a unified explanation for the appearance of Wenckebach, reverse Wenckebach, alternating Wenckebach, and high grade block rhythms.

Torsade de pointes ventricular tachycardia in a hypothyroid patient treated with propafenone.

A 31-year-old female had recurring palpitations and black-outs for 13 years. Hyperthyroidism was diagnosed and electrocardiogram suggested ventricular preexcitation. Despite being treated for hyperthyroidism (which rendered the patient hypothyroid) and receiving propranolol for the arrhythmia, the palpitations persisted. Electrophysiologic testing identified the patient's arrhythmia, and demonstrated that it improved with intravenous propafenone, a new type 1C antiarrhythmic medication. After two days of oral propafenone, this initially good response was followed by episodes of Torsade de pointes ventricular tachycardia with repeated cardiac arrest. Lidocaine and isoproterenol failed to control the rhythm, and the patient was stabilized by electrical cardioversions, atrial pacing and withdrawing the propafenone. Propafenone has been used to treat Torsade de pointes, but we show that it may also cause Torsade de pointes.

Is high potassium solution necessary for reinfusions in "multidose" cold cardioplegia? A randomized prospective study using computerized Holter system.

Multidose potassium cardioplegia is a common method of myocardial preservation. Although initial potassium arrest conserves high-energy phosphates, there is conflicting evidence that repeat high potassium boluses augment this protection. Fifty-six patients were prospectively randomized to receive multidose cold high potassium cardioplegia (27 mEq of KCl/L) both in the initial and subsequent infusions (Group 1) or an initial cold high potassium (27 mEq/L) cardioplegia followed by boluses of cold low potassium (7 mEq, of KCl/L) solution (Group 2). The two groups were compared in terms of postoperative myocardial electrical stability and hemodynamic performance. Electrocardiograms were recorded by continuous Holter monitor, and the data were analyzed by computer. The duration of aortic cross-clamping and cardiopulmonary bypass did not differ between groups. Group 1, who received more total KCl than Group 2 (p less than .005), experienced more high-grade ventricular ectopia during both reperfusion (p less than .001) and the immediate postoperative period (p less than .001), and required more lidocaine hydrochloride (p less than .001) for arrhythmias. There was no significant difference in hemodynamic performance between the two groups. This study fails to show an advantage to multidose "high potassium" cardioplegia and found a significant increase in ventricular ectopia associated with its use. We advocate using low potassium solutions after initial cold high potassium arrest.

Reuse of permanent cardiac pacemakers.

Cardiac pacemakers are part of a growing group of expensive implantable electronic devices; hospitals in which 100 pacemakers are implanted per year must budget over $300 000 for these devices. This cost represents a considerable burden to health care resources. Since the "life-span" of modern pacemakers often exceeds that of the patients who receive them, the recovery and reuse of these devices seems logical. Pacemakers can be resterilized and tested with current hospital procedures. Reuse should be acceptable under Canadian law, but the manner in which the pacemakers are recovered and the patients selected should follow careful guidelines. Every patient should provide written informed consent before receiving a recovered pacemaker. Properly executed, reuse of pacemakers should provide a high level of health care while maintaining or reducing the cost of these devices.

Perioperative Holter monitoring and computer analysis of dysrhythmias in cardiac surgery.

In order to increase the accuracy and efficiency of studying perioperative dysrhythmias, 52 patients undergoing cardiac surgery were fitted preoperatively with a Holter monitor adapted for intraoperative recording, and the preoperative, intraoperative and early postoperative cardiac electrical activities were classified with a digital computer. Forty patients underwent coronary artery bypass grafting (CABG), eight had valve replacements, and four had combined procedures. The results showed the following: (1) high incidence of various dysrhythmias occurring during anesthesia induction and thoracotomy prior to aortic cross-clamp; (2) high incidence of continued atrial activity during cardioplegia; (3) lack of correlation between peak serum CPK-MB levels and dysrhythmias; and (4) a higher overall incidence of dysrhythmias in valve patients. Adapting the Holter monitor technique for cardiac surgery can solve the problem of observer vigilance inherent to such a study using a human "monitor watcher," and facilitate the accurate analysis of the vast amount of data obtained. This is important in quantitating the electrophysiologic effects of various perioperative interventions, such as the anesthetic agents, beta-blockers, calcium antagonists, and cardioplegic solutions.

A comparative trial of the antidepressant, anxiolytic, and cardiovascular effects of trimipramine and doxepin in depressed hospitalized patients.

After a 1-week placebo washout, 25 depressed hospitalized patients were treated for 4 weeks with trimipramine or doxepin in a fixed equivalent dosage schedule ending in 150 mg h.s. The study used a parallel group double-blind design. Comparisons over time revealed that both drugs improved patients' overall well-being as indicated by the rating scales studied. Significant (p less than .05) differences between the treatments favored trimipramine over doxepin: the Hamilton scale diurnal variation cluster at Week 1 and the sleep disturbance factor at Week 4; the Clinical Global Impressions improvement index at Week 1; and the Anxiety Status Inventory somatic symptoms cluster at Week 4. No differences in blood pressure, heart rate, PVCs, or PACs were observed in any of the comparisons. The total number of side effects reported was greater in the doxepin-treated patients.

Artificial cardiac stimulation: a current view of physiologic pacemakers.

Artificial pacing of the heart has evolved rapidly over the last 20 years; the physician can now implant "physiologic" pacemakers that preserve the natural order of atrial and ventricular systole. The commonly used pacemakers that pace only the ventricle can induce dizziness, fatigue and syncope and increase congestive heart failure. Physiologic pacemakers can eliminate many of these side effects, but they are more expensive, can be less durable and may induce arrhythmias. Physiologic pacing can provide the greatest benefit and cost-effectiveness when the particular functions of the device are matched to the specific needs of the patient.

Role of sympathetic nervous system in non-ischaemic ventricular arrhythmias.

Propranolol and nadolol were used in two groups of patients having ventricular arrhythmias. The two groups were characterised by differences in sympathetic drive. The 10 non-adrenergic patients had idiopathic, monomorphic extrasystoles (isolated with fixed coupling or in pairs or salvoes) arising from the right ventricle or the septum. These extrasystoles were chronic and benign, with a slightly increased daytime frequency (day:night = 1.6). They disappeared on exercise. The nine adrenergic patients had less frequent but more complex polymorphic ventricular extrasystoles, and rapid and irregular tachycardias which were resistant. They occurred predominantly during the day and were associated particularly with stress and exercise. They were either idiopathic, or coexisted with mitral valve prolapse (three cases) or hypertrophic subaortic stenosis (one case) in young patients (mean age, 32 years) who did not have coronary heart disease. Nadolol was more effective than propranolol in controlling the arrhythmia, heart rate, and variations in sinus rhythm in the adrenergic group, while the arrhythmia was not controlled in the non-adrenergic group. Using clinical variables, comparison of the frequency of extrasystoles by day and night, and assessment of the antiarrhythmic effect of beta-blockers, the role of the sympathetic tone in non-ischaemic ventricular arrhythmias may be elucidated.