Comparison of cardiac pacing modes in patients with chronic obstructive pulmonary disease.

STUDY OBJECTIVE: This study compares the relative benefits of dual chamber adaptive rate pacing (DDDR) with ventricular adaptive rate pacing (VVIR) in patients with chronic obstructive pulmonary disease (COPD). STUDY DESIGN: Cardiac hemodynamics were evaluated with serial exercise tests. A minimum of 2 h was allowed between studies. Pulmonary gas exchange was measured and cardiac output (CO) was determined at rest and immediately after maximum exercise by Doppler echocardiography. PATIENTS: Sixteen patients with DDDR pacemakers were studied. Eight patients had COPD and eight patients had normal lung function (NLF). Baseline lung function was documented with spirometry. INTERVENTIONS: The patients with NLF functioned as a control group. Prior to entry into the study, the rate-modulated parameters of the pacemaker were programmed to a clinically determined optimal set of parameters for each individual patient. These were not changed for the duration of the study. RESULTS: Both groups showed a statistically significant improvement in exercise duration, CO at maximum exercise, and cardiac output difference (CODiff) with the dual chamber adaptive rate pacing mode (DDDR). (COdiff is the change in CO from rest to maximum exercise.) Patients with NLF also showed a significant improvement in anaerobic threshold (AT) and VCO2 max with DDDR. Patients with lung disease showed a statistically significant improvement at all levels of exercise in the ventilatory equivalent for oxygen. CONCLUSION: In this study, those patients with chronic lung disease who required cardiac pacing performed significantly better in the DDDR mode as compared with the VVIR mode. Therefore, the DDDR pacing mode should provide an improved quality of life for the patient with COPD who also requires cardiac pacing.

The origin of lipofuscin and possible consequences to the myocardium.

Examination by light and electron microscopy of human myocardium from necropsies and biopsy specimens has revealed evidence that mitochondria can be transformed into granules of lipofuscin. This pigment has been shown to arise from peroxidative destruction of polyunsaturated lipid membranes. A high rate of lipofuscin formation is indicated by the occurrence of brown atrophy of the heart in relatively young persons who died of conditions that were associated with inanition. Such lipofuscin formation suggests the importance of dietary antioxidants in preventing peroxidative damage to mitochondria. A by-product of lipid peroxidation, malonaldehyde, can react with nuclear DNA, blocking template activity. Nuclear damage of this kind could reduce the capacity for protein synthesis and limit mitochondrial and contractile protein replacement. Such a limitation would contribute to heart failure during stress. Peroxidative damage to the myocardium is cumulative and irreversible.

Cardiac myxomas: report of eight cases with successful excision.

Early diagnosis of atrial myxoma can be made by a high index of suspicion in patients in whom embolic phenomena, systemic manifestations, syncope, or suspected mitral or tricuspid valvular disease are noted. When the presence of an atrial myxoma is suspected, echocardiographic evaluation should be done promptly. This noninvasive technique has no morbidity or mortality and is accurate in greater than 90 percent of cases.

Deriving the 12-lead electrocardiogram from four (EASI) electrodes.

Computerized interpretation of the electrocardiogram has now advanced to computerization of the electrocardiograph, resulting in greatly increased versatility, including the capacity for adapting to a variety of lead systems rather than being tethered to the old Einthoven-Wilson-Goldberger (EWG) system. Many varieties of display beyond the 12-lead ECG are also available in software. To date, these new and interesting capabilities have scarcely been exploited. The EASI lead system uses the E, A, and I electrode positions of the Frank lead system, plus an electrode, S, positioned over the upper end of the sternum and, if necessary, ground (anywhere convenient). Its outputs form quasi-xyz signals, x'y'z', that can be approximately transformed into xyz signals by means of a matrix derived from the EASI lead vectors. The result forms a good basis for deriving the 12-lead ECG, using previously published coefficients for the Frank lead system. The match with the conventional ECG can then be improved by statistical means. The results are surprisingly good, and certainly of clinical value. Recent widespread interest in silent ischemia and its detection through Holter monitoring suggests an immediate application which has been rendered practical by the recent introduction of three-channel recorders. The EASI electrode positions give technically satisfactory Holter recordings. Very compact three-channel, multiplexed, radio telemetry equipment is now commercially available and provides another application for the EASI 12-lead ECG.(ABSTRACT TRUNCATED AT 250 WORDS)

Pericardial closure and paradoxic septal motion after surgery.

We tested the role of the pericardium in the development of paradoxic septal motion in 29 patients by analyzing M-mode echocardiograms made before and after cardiac surgery. Surgical technic was the same for all patients, but the pericardium was closed by random selection in 12 (40%). Paradoxic septal motion developed in five of the 12 patients (42%) with a sutured pericardium and in 11 of 17 (65%) whose pericardium was not closed (chi-square not significant). Septal motion measured 7.3 +/- 3.3 mm before and -0.6 +/- 4.6 mm after surgery (P less than .001), with a similar degree of impairment for both groups. An echographically derived ejection fraction changed from 71 +/- 9% before to 60 +/- 13% after surgery (P less than .001). We conclude that leaving the pericardium open has no particular role in the development of paradoxic septal motion. Septal motion diminished in all. Changed in the echo ejection fraction could represent an impairment in ventricular function.

Comparison of intrinsic versus paced ventricular function.

UNLABELLED: There is increasing evidence supporting the benefits of providing optimum AV delay in cardiac pacing, though controversy exists regarding its value and the benefits of intrinsic versus paced ventricular activation. This study compared various AV delays at rest in patients whose native AV delays were > or = 200 msec. Only patients with DDD pacemakers who had intact AV conduction and normal ventricular activation were included in the study. Nine patients were studied. METHODS: Ten studies were performed. Evaluation was done in AAI and DDD modes at paced heart rates of 60/min or as close as possible to the intrinsic heart rate if this was > 60/min. Stroke volume (SV) and cardiac output (CO) were measured. RESULTS: When AV sequential pacing in the DDD mode with an optimum AV delay was compared to AAI pacing with a prolonged AV interval, the average optimum AV delay in the DDD mode was 157 msec and ranged from 125 to 175 msec. The average AV interval in the AAI mode was 245 msec and ranged from 212 to 300 msec. In the DDD mode, there was an overall significant improvement in CO of 11% and SV of 9%. Patients with intrinsic AV conduction times of > 220 msec showed an overall significant improvement in CO of 13% and SV of 11%. In patients with intrinsic AV conduction times of < 220 msec, an improvement in CO of 6% and SV of 4% was seen. CONCLUSIONS: (1) An optimum AV delay is an important component of hemodynamic performance; and (2) AV sequential pacing at rest with an optimum AV delay may provide better hemodynamic performance than atrial pacing with intrinsic ventricular conduction when native AV conduction is prolonged > 220 msec.

Cardiac pacemakers in pediatric heart transplant recipients: incidence, indications, and associated factors. Pediatric Heart Transplant Group-Loma Linda.

This study was undertaken to assess the incidence, indications, and predisposing factors for pacemaker placement in a pediatric heart transplant population. From November 1985 to May 1994, 246 pediatric patients have undergone cardiac transplantation at Loma Linda University Medical Center. Seven (2.8%) have received pacemaker placement with an 8-50 month follow-up period. Median age at transplant was 462 days (0 days to 2.5 years). The median time to pacemaker placement was 190 days (18-1,672 days) after transplantation. Indications were sick sinus syndrome (SSS) in 5 and heart block in 2 patients (1 during acute rejection). Three patients with SSS underwent electrophysiology studies (EPS); 1 was normal and 2 showed sinus node dysfunction. The mode of pacing was VVIR in 6 patients and VVI in 1 patient. All 6 survivors are doing well and 5 patients' pacemakers still provide support. These 7 patients were compared with 185 pediatric patients (0 days to 12-years-old) transplanted during 1985 through 1993 who survived at least 6 months after transplantation. There was no correlation between the receipt of a pacemaker and graft cold ischemic time, rejection history, donor age, or recipient age at transplantation. The 5 patients with SSS had significantly lower average heart rates in the first month after transplantation (108 +/- 16 vs 130 +/- 12; P = 0.0002). The need for permanent pacemakers in this population is uncommon. Pacemakers, however, can be safely performed when necessary with excellent clinical results.

Comparative evaluation of rate modulated dual chamber and VVIR pacing.

While dual chamber pacing is considered superior to VVI pacing at rest, there is a continuing debate as to the relative benefit of AV synchrony versus rate increase with exercise. To evaluate this question and to correlate different methods of evaluation, 14 patients with DDDR pacemakers were studied using serial treadmill exercise test with a CAEP protocol. Patients were exercised in DDD, DDDR, and VVIR modes. Echo-Doppler cardiac outputs were determined and pulmonary gas exchange was measured during exercise. There was a significant improvement in cardiac output with exercise in the DDDR versus VVIR modes, and in DDDR versus DDD modes in patients with chronotropic incompetence. There were small increases in exercise duration in DDDR versus VVIR modes, and small but consistent increases in VO2 at all levels of exercise, though not statistically significant. In this group of patients, DDDR pacing was superior to VVIR pacing, and superior to DDD pacing when chronotropic incompetence was present.