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R S Bubien

Publications and source records attributed to R S Bubien.

17 recordsLinked to original sources
PubMed2001

Atrial fibrillation: treatment rationale and clinical utility of nonpharmacologic therapies.

Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia requiring therapy. Nonpharmacologic therapies for the treatment of AF, namely, catheter ablation, cardiac pacing, internal defibrillation, and dysrhythmia surgery are playing an increasingly important role in the overall management of AF. Although usually prescribed when traditional pharmacologic therapy is not effective, not tolerated, or contraindicated, these therapies are rapidly assuming a more prominent role as they mature. These modern therapies for AF, offering the promise of prevention and cure of AF, potential elimination from the sequelae of AF, and significant improvements in quality of life, are increasingly becoming more frequent in clinical practice. Further investigation is needed to determine which therapy is ideally suited for an individual patient and the impact of these varying therapies on morbidity and mortality.

Atrial Fibrillation↗
PubMed1999

Mode switching in dual chamber pacemakers: effect of onset criteria on arrhythmia-related symptoms.

AIMS: Various mode-switching algorithms are available with different tachyarrhythmia detection criteria to be satisfied to initiate mode-switching. This study evaluated three different mode-switching algorithms in patients with paroxysmal atrial fibrillation. METHODS AND RESULTS: Seventeen patients completed the study. Three mode-switching algorithms were downloaded as software into the pacemaker, each for 1 month in a single-blind, randomized sequence. The criteria to initiate mode-switching were: mean atrial rate ('standard'), '4-of-7' or '1-of-1' atrial intervals to exceed the atrial detection rate. Symptoms for each were measured using the Symptom Checklist Frequency and Severity index. The median number of mode-switch episodes increased from 20 for 'standard' to 39 for '4-of-7' (P=0.029 vs 'standard') and 103 for '1-of-1' (P=0.0012 vs 'standard') onset criteria. Median duration of episodes decreased from 2.5 min with 'standard' to 1.4 min with '4-of-7' and 0.4 min with '1-of-1' onset criteria. Frequency of symptoms was lower using '4-of-7' (18.2 +/- 12.0 vs 23 +/- 12.0, P=0.08) or '1-of-1' (20.4 +/- 12.4 vs 23 +/- 12.0, P=0.07) than 'standard' onset criteria. Severity of arrhythmia tended to be less with either '4-of-7' (16 +/- 10.4 vs 19.1 +/- 19.4, P=0.12) or '1-of-1' (17.5 +/- 10.3 vs 19.1 +/- 9.4, P=0.18) than with 'standard' onset criteria. CONCLUSIONS: The more sensitive onset criteria for detection of atrial tachyarrhythmias were associated with lower frequency and severity of symptoms.

Algorithms↗
PubMed1998

NASPE expert consensus document: use of i.v. (conscious) sedation/analgesia by nonanesthesia personnel in patients undergoing arrhythmia specific diagnostic, therapeutic, and surgical procedures.

Use of IV (Conscious) Sedation/Analgesia by Nonanesthesia Personnel in Patients Undergoing Arrhythmia Specific Diagnostic, Therapeutic, and Surgical Procedures. This article is intended to inform practitioners, payers, and other interested parties of the opinion of the North American Society of Pacing and Electrophysiology (NASPE) concerning evolving areas of clinical practice or technologies or both, that are widely available or are new to the practice community. Expert consensus documents are so designated because the evidence base and experience with the technology or clinical practice are not yet sufficiently well developed, or rigorously controlled trials are not yet available that would support a more definitive statement. This article has been endorsed by the American College of Cardiology, October 1997.

Anesthesiology↗
PubMed1998

The effect of maximum heart rate on oxygen kinetics and exercise performance at low and high workloads.

The normal heart rate is linearly related to oxygen consumption during exercise. The maximum heart rate of the normal sinus node is approximated by the formula: HRmax = (220-age) with a variance of approximately 15%. However, the nominal upper rate of most permanent pacemakers is 120 beats/min, a value that remains unchanged for many patients. As this nominal setting falls well below the maximum predicted heart rate for most patients, it is possible that the chronotropic response of rate adaptive pacemakers during moderate and maximal exercise workloads may be less than optimal. The purpose of this study was to determine the effect of the upper programmed rate on oxygen kinetics during submaximal exercise workloads and maximum exercise performance during symptom-limited treadmill exercise. Exercise performance with an upper rate programmed to 220-age was compared with an upper rate of 120 beats/min. Eleven patients (5 men and 6 women, mean age 54 +/- 10 years) with complete heart block following catheter ablation of the atrioventricular junction for refractory atrial fibrillation who were implanted with permanent, rate-modulating VVIR pacemakers comprised the study population. The rate adaptive sensors were based on activity in 8 patients, minute ventilation in 2 patients, and mixed venous oxygen saturation in 1 patient. After performing a symptom-limited treadmill exercise test to determine maximum exercise capacity and to optimized programming of the rate adaptive sensor, each subject performed two treadmill exercise tests in random sequence with a rest period of at least 1 hour between tests. During one of the tests the upper rate was programmed to a value calculated by the formula: HRmax = (220-age). During the other exercise test the upper rate was programmed to 120 beats/min. Patients were blinded as to their programmed values and to the hypothesis of the study. A novel treadmill exercise protocol was used that consisted of a 6 minute, constant-workload phase at approximately 50% of maximum workload followed immediately by incremental, symptom-limited exercise using a modified Chronotropic Assessment Exercise Protocol(CAEP) with 1 minute stages until; peak exertion. Breath-by-breath analysis of expired gases was performed with subjective scoring of exertional difficulty at the end of the constant workload phase and during each stage of incremental exercise using the Borg Perceived Exertion Scale. Exercise duration was significantly longer (637 +/- 47 vs 611 +/- 48 seconds, P < 0.005) with the higher programmed upper rate. Oxygen kinetics were also significantly improved with an age predicted upper rate with a lower O2 deficit (258 +/- 88 vs 395 +/- 155 mL, P = 0.002) and higher VO2 rate constant (3.6 +/- 1.0 vs 2.4 +/- 0.7, P < 0.001). The VO2max during peak exertion was higher with an age predicted upper rate than with an upper rate of 120 beats/min (1807 +/- 751 vs 1716 +/- 702 mL/min, P = 0.04). The mean Borg score was lower during the last common treadmill stage during maximum exercise with an age predicted upper rate than with an upper rate of 120 beats/min (15.7 +/- 2.0 vs 16.5 +/- 1.9, P = 0.04). The mean Borg score during submaximal, constant workload exercise was also lower with a higher upper rate (9.0 +/- 2.5 vs 9.6 +/- 2.2, P = 0.10). Programming the upper rate of rate adaptive pacemakers based on the age of the patient improves exercise performance and exertional symptoms during both low and high exercise workloads as compared with a standard nominal value of 120 beats/min.

Adult↗
PubMed1998

Two-year experience with rate-modulated pacing controlled by mixed venous oxygen saturation.

Mixed venous oxy-hemoglobin saturation (MVO2) is a physiological variable with several features that might be desirable as a control parameter for rate adaptive pacing. Despite these desirable characteristics, the long-term reliability of the MVO2 sensor in vivo is uncertain. We, therefore, designed a study to prospectively evaluate the long-term performance of a permanently implanted MVO2 saturation sensor in patients requiring VVIR pacing. Under an FDA approved feasibility study, eight patients were implanted with a VVIR pulse generator and a right ventricular pacing lead incorporating an MVO2 sensor. In order to accurately assess long-term stability of the sensor, patients underwent submaximal treadmill exercise using the Chronotropic Assessment Exercise Protocol (CAEP) at 2 weeks, 6 weeks, and 3, 6, 9, 12, 18, and 24 months following pacemaker implantation. Paired maximal exercise testing using the CAEP was also performed with the pacing system programmed to the VVI and VVIR modes in randomized sequence with measurement of expired gas exchange after 6 weeks and 12 months of follow-up. During maximal treadmill exercise the peak exercise heart rate (132 +/- 9 vs 71.5 +/- 5 beats/min, P < 0.00001) and maximal rate of oxygen consumption (1,704 +/- 633 vs 1382 +/- 407 mL/min, P = 0.01) were significantly greater in the VVIR than in the VVI pacing mode. Similarly, the duration of exercise was greater in the VVIR than the VVI pacing mode (8.9 +/- 3.6 min vs 7.6 +/- 3.7 min, P = 0.04). The resting MVO2 and the MVO2 at peak exercise were similar in the VVI and VVIR pacing modes (P = NS). However, the MVO2 at each comparable treadmill exercise stage was significantly higher in the VVIR mode than in the VVI mode (CAEP stage 1 (P = 0.005), stage 2 (P = 0.04), stage 3 (P = 0.008), and stage 4 (P = 0.04). The correlation between MVO2 and oxygen consumption (VO2) was excellent (r = -0.93). Telemetry of the reflectance of red and infrared light and MVO2 in the right ventricle during identical exercise workloads revealed no significant change over the first 12 months of follow-up (ANOVA, P = NS). The chronotropic response to exercise remained proportional to VO2 in all patients over the first 12 months of follow-up. The time course of change in MVO2 during maximal exercise was significantly faster than for VO2. At the 18- and 24-month follow-up exercise tests, a significant deterioration of the sensor signal with attenuation of chronotropic response was noted for 4 of the 8 subjects with replacement of the pacing system required in one patient because of lack of appropriate rate modulation. Rate modulated VVIR pacing controlled by right ventricular MVO2 provides a chronotropic response that is highly correlated with VO2. This parameter responds rapidly to changes in workload with kinetics that are more rapid than those of VO2. Appropriate rate modulation provides a higher MVO2 at identical workloads than does VVI pacing. Although the MVO2 sensor remains stable and accurate over the first year following implantation, significant deterioration of the signal occurs by 18-24 months in many patients.

Adult↗
PubMed1996

Effect of radiofrequency catheter ablation on health-related quality of life and activities of daily living in patients with recurrent arrhythmias.

BACKGROUND: Although radiofrequency catheter ablation can be used to effectively treat a variety of arrhythmias, the effects of this procedure on health-related quality of life have not been systematically studied. METHODS AND RESULTS: The SF-36 (a measure of general health status), the Symptom Checklist-Frequency and Severity Scale (an instrument specific for cardiac arrhythmias), and an Activities of Daily Living questionnaire were used to assess quality of life in 161 patients before radiofrequency catheter ablation. These same instruments were used to measure quality of life 1 and 6 months after ablation with complete data in 159 of the original 161 patients. Before ablation, SF-36 scores of the study population were low compared with the US normative data base reflecting significant impairment in physical functioning and well-being. The lowest scores were reported by patients with atrial fibrillation and atrial flutter. Catheter ablation was associated with significant improvement in quality of life that was sustained over the 6 months after ablation. Improvements were measured in both the generic SF-36 health status questionnaire and the disease-specific Symptom Checklist-Frequency and Severity Scale. Catheter ablation was followed by improved performance of activities of daily living and a marked decrease in the number of visits to physicians and emergency rooms in the 6 months after ablation compared with the 6 months before ablation. CONCLUSIONS: Radiofrequency catheter ablation improves the health-related quality of life for patients with a variety of cardiac arrhythmias.

Activities of Daily Living↗
PubMed1996

Quality of life in patients with atrial fibrillation.

Quality of life is discussed with focus on the importance of individual patient perspectives. Eight studies including at least one aspect of quality of life in patients with atrial fibrillation are reviewed with three approaches evident in assessing quality of life: patient interview, self-reported symptoms, and multidimensional assessment. What has been learned about quality of life to date has been from generally highly symptomatic patients refractory to traditional pharmacotherapy; no studies describe quality of life in minimally symptomatic patients with atrial fibrillation. Rationale for extending this knowledge is discussed.

Atrial Fibrillation↗
PubMed1995

Relationship between heart rate and oxygen kinetics during constant workload exercise.

BACKGROUND: Oxygen uptake during constant workload exercise increases exponentially from its resting value before reaching a steady state. The difference between the actual rate of oxygen consumption at the onset of exercise and the steady state is an oxygen deficit. Similarly, the normal sinus node increases its rate at the onset of exercise before achieving a steady state, thereby producing a heart rate deficit. The purpose of this study was to test the hypothesis that elimination of the heart rate deficit by an instantaneous increase in heart rate at the onset of constant workload exercise to the steady-state level would reduce the oxygen deficit and improve the perceived difficulty of exertion as compared with the chronotropic response of the normal sinus node. METHODS AND RESULTS: Ten subjects with normal sinus node function who had DDD pacemakers implanted for AV block completed a symptom-limited maximal treadmill exercise test using the Chronotropic Assessment Exercise Protocol (CAEP) to assess sinus node function, maximal heart rate, and VO2max. The subjects then performed constant workload exercise tests (6-min duration) at a workload equal to approximately 50% of metabolic reserve with the pacemaker randomly programmed to each of three patterns of chronotropic response: (1) DDD (lower rate 60 beats/min); (2) Fast (lower rate abruptly programmed to the expected value at 50% metabolic reserve); and (3) Overpaced (lower rate at least 80% of the age predicted maximum). The oxygen deficit was lower with the fast chronotropic response (434 +/- 238 mL O2) than with either the DDD (512 +/- 233; P = 0.02), or overpaced chronotropic patterns (488 +/- 238; P = 0.02 vs fast). The rate constant for change in VO2 was highest with the fast chronotropic pattern (2.85 +/- 1.38) compared with either the DDD (2.25 +/- 0.64; P = 0.01) or overpaced (2.38 +/- 0.43; P = 0.02) patterns. The Borg perceived exertion rating was lowest with the fast chronotropic response (P = 0.02 vs DDD and P = 0.02 vs overpaced). CONCLUSIONS: The results of this study suggest that oxygen kinetics and exertional symptoms are improved by an abrupt increase in pacing rate at the onset of exercise to a value that is appropriate for metabolic demand as compared with the DDD pacing mode in patients with normal sinus node function. In contrast, an overly aggressive chronotropic response was not associated with improved oxygen kinetics or exertional symptoms.

Adult↗
PubMed1994

Effect of chronotropic response pattern on oxygen kinetics.

BACKGROUND: The sinus node is considered to be the model of chronotropic response for pacemakers that use artificial rate modulating sensors. Maximal metabolic exercise testing with measurement of oxygen consumption (VO2) is frequently used to evaluate chronotropic response. Since activities of daily living are generally transient and involve submaximal effort, maximal exercise testing may not provide the most clinically relevant method of assessing rate modulation. The purpose of this study was to determine if an abrupt increase in heart rate (HR) at the onset of submaximal exercise provides improved oxygen kinetics compared with a linear response. METHODS AND RESULTS: Thirteen patients with complete heart block and permanent rate modulating pacemakers implanted following catheter ablation of the atrioventricular junction for refractory atrial fibrillation were chosen for study. The patients first completed a maximal treadmill exercise test using the chronotropic assessment exercise protocol with breath-by-breath analysis of expired gases. The expected HR at 50% of metabolic reserve was calculated for each patient. Three submaximal constant workload exercise tests were then performed at 50% of each patient's metabolic reserve, with the pacemaker randomly programmed to provide three different patterns of chronotropic response: linear (in which HR increased from 70 beats/min to the expected HR at 50% of metabolic reserve), fast (in which HR was abruptly increased to the expected HR at 50% of metabolic reserve), and slow (VVI at 70 beats/min). Oxygen kinetics were compared for the three patterns of chronotropic response. Cumulative oxygen (O2) consumption was significantly greater for the fast pattern (3610 mL) as compared with the linear (3487 mL, P = 0.004) or slow pattern (3277 mL). The O2 deficit was lower for the fast (361 +/- 139 mL) than for the linear (539 +/- 225 mL, P = 0.003) or slow chronotropic pattern (559 +/- 194). Similar improvements in the rate constant of O2 uptake and Borg perceived exertion scores were observed with the fast chronotropic response pattern. CONCLUSION: A rapid increase in pacing rate at the onset of exercise improves oxygen kinetics and results in less perceived exertion as compared to a more gradual rate increase that is more characteristic of sinus node behavior.

Adult↗
PubMed1994

Rate modulated pacing based on right ventricular dP/dt: quantitative analysis of chronotropic response.

Right ventricular contractility increases in response to catecholamine stimulation and greater ventricular preload, factors that increase with exercise workload. Thus, the maximum systolic dP/dt may be a potentially useful sensor to control the pacing rate of a permanent pacing system. The present study was designed to test the long-term performance of a permanent pacemaker that modulates pacing rate based on right ventricular dP/dt and to quantitatively analyze the chronotropic response characteristics of this sensor in a group of patients with widely varying structural heart diseases and degrees of hemodynamic impairment. A permanent pacing system incorporating a high fidelity pressure sensor in the lead for measurement of right ventricular dP/dt was implanted in 13 patients with atrial arrhythmias and AV block, including individuals with coronary artery disease, hypertension, severe obstructive pulmonary disease with prior pneumonectomy, atrial septal defect, dilated cardiomyopathy, restrictive cardiomyopathy, and mitral stenosis. Patients underwent paired treadmill exercise testing in the VVI and VVIR pacing modes with measurement of expired gas exchange and quantitative analysis of chronotropic response using the concept of metabolic reserve. The peak right ventricular dP/dt ranged from 238-891 mmHg/sec with a pulse pressure that ranged from 19-41 mmHg. There was a positive correlation between the right ventricular dP/dt and pulse pressure (r = 0.70, P = 0.012). The maximum pacing rate and VO2max were 72 +/- 6 beats/min and 12.61 +/- 4.0 cc O2/kg per minute during VVI pacing and increased to 124 +/- 18 beats/min and 15.89 +/- 5.9 cc O2/kg per minute in the VVIR pacing mode (P < 0.0003 and P < 0.002, respectively). The integrated area under the normalized rate response curve was 96.7 +/- 45.7% of expected during exercise and 100.1 +/- 43.4% of expected during recovery. One patient demonstrated an anomalous increase in pacing rate in response to a change in posture to the left lateral decubitus position. Thus, the peak positive right ventricular dP/dt is an effective rate control parameter for permanent pacing systems. The chronotropic response was proportional to metabolic workload during treadmill exercise in this study population with widely varying forms of structural heart disease.

Adult↗
PubMed1992

Intracoronary ethanol ablation for the treatment of recurrent sustained ventricular tachycardia.

The selective infusion of ethanol into the coronary circulation supplying the site of origin of incessant ventricular tachycardia has been demonstrated to abolish this arrhythmia in selected patients. The present study was designed to evaluate the efficacy and safety of the intracoronary ethanol ablation technique in patients with paroxysmal ventricular tachycardia related to prior myocardial infarction. Twenty-three patients with sustained monomorphic ventricular tachycardia that was refractory to conventional antiarrhythmic drug therapy were prospectively studied. After induction of ventricular tachycardia by programmed electrical stimulation, the response of the arrhythmia to the infusion of radiographic contrast medium or saline solution into the ostia of the native coronary arteries and coronary artery bypass grafts was assessed. If ventricular tachycardia was reliably interrupted by injections into the proximal coronary artery or bypass graft, the vessel was cannulated with a steerable guide wire and 2.7F infusion catheter to determine the smallest arterial branch that would result in termination of the arrhythmia with selective injections. If reliable interruption of ventricular tachycardia was observed with saline or contrast injections, ethanol (2 ml) was then delivered through the infusion catheter. Ventricular tachycardia could be terminated by injections of saline solution or contrast medium in 11 of 21 patients in whom the protocol could be completed. Ethanol was infused in 10 of these patients. Ventricular tachycardia was inducible in only 1 of 10 patients immediately after ethanol infusion. At a follow-up electrophysiologic study performed 5 to 7 days after ablation, ventricular tachycardia became inducible in two other patients, in one of whom the arrhythmia substrate was successfully ablated after three sessions. The mean left ventricular ejection fraction was 0.33 +/- 0.1 before and 0.35 +/- 0.11 after ablation. Complications of the procedure included complete atrioventricular block in four patients and pericarditis in one patient. Thus, intracoronary ethanol ablation is associated with a moderate degree of efficacy but the potential for important complications. Despite these limitations, this technique may provide effective long-term control of ventricular tachycardia for some patients.

Aged↗
PubMed1991

A prospective evaluation of intracoronary ethanol ablation of the atrioventricular conduction system.

The clinical efficacy and complications associated with ablation of the atrioventricular (AV) conduction system by the selective infusion of ethanol into the AV node artery were prospectively assessed in 12 consecutive patients with medically refractory atrial arrhythmias. Six of the patients had previously failed to have permanent complete AV block created with direct current or radiofrequency catheter ablation. The AV node artery was cannulated with a 0.016 in. (0.041 cm) guide wire in all 12 patients. It was also possible to advance a 2.7F infusion catheter into the AV node artery in all patients. Transient AV block was induced by selective injections into the AV node artery of iced saline solution (8 patients) and of radiographic contrast agent (ioxaglate) (10 patients). The infusion of 2 ml of ethanol (96%) induced immediate complete AV block in all 10 patients who demonstrated AV block with ioxaglate. The escape rhythm exhibited a narrow QRS complex preceded by a His bundle deflection in nine patients and left bundle branch block in one patient. The immediate mean rate of the escape rhythm was 45.3 +/- 13.4 beats/min. In two patients who demonstrated reflux of contrast agent into the distal right coronary artery with selective injections into the AV node artery, transient ST segment elevation developed in the inferior electrocardiographic leads with the infusion of ethanol. There was no change in the left ventricular ejection fraction from the baseline value (0.53 +/- 0.12) to that measured after ablation (0.55 +/- 0.11) and no patient developed wall motion abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Rate-modulated cardiac pacing based on transthoracic impedance measurements of minute ventilation: correlation with exercise gas exchange.

The relation of pacing rate to physiologic variables of metabolic demand was examined in 10 consecutive patients with a minute ventilation-sensing, rate-modulating ventricular pacemaker implanted for complete heart block. All patients had paroxysmal (seven patients) or chronic (three patients) atrial fibrillation and were referred for catheter ablation of the atrioventricular junction. Treadmill exercise testing with measurement of expired gas exchange and respiratory flow was performed before ablation and 4 weeks after pacemaker implantation, with the pacemaker programmed to both the fixed-rate VVI and rate-modulating minute ventilation VVIR pacing modes in random sequence. The relation of pacing rate to oxygen consumption (VO2), expired carbon dioxide concentration (VCO2), respiratory quotient, tidal volume, respiratory rate and minute ventilation was determined during exercise in the rate-modulating minute ventilation pacing mode. Pacing rate was highly correlated with minute ventilation (r = 0.89), respiratory quotient (r = 0.89), VCO2 (r = 0.87), tidal volume (r = 0.87), VO2 (r = 0.84) and respiratory rate (r = 0.84). The mean exercise duration increased from 8.3 +/- 2.8 min in the fixed rate pacing mode to 10.2 +/- 3.4 min in the rate-modulating, minute ventilation mode (p = 0.0001). The maximal VO2 increased from 13.4 +/- 3.4 to 16.3 +/- 4.1 cc/kg per min (p = 0.0004). The maximal heart rate achieved in the minute ventilation pacing mode was 136 +/- 9.7 beats/min, similar to that observed in the patient's intrinsic cardiac rhythm before ablation (134.9 +/- 30.1 beats/min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Effect of catheter ablation of the atrioventricular junction on quality of life and exercise tolerance in paroxysmal atrial fibrillation.

The effect of catheter ablation of the atrioventricular junction (AV) and implantation of a rate-adaptive pacemaker on quality of life and exercise capacity was evaluated prospectively in 12 consecutive patients with paroxysmal atrial fibrillation (AF). All patients had been demonstrated to have paroxysmal AF that was refractory to medical therapy over a long period of time (mean 9 +/- 7 years). Patients performed a symptom-limited treadmill exercise test on the day before catheter ablation and 6 weeks after hospital discharge. Quality of life was measured using the physical dimension of the McMaster Health Index Questionnaire and the Psychological General Well-Being Index before and 6 weeks after ablation. There were no serious complications related to catheter ablation or permanent pacemaker implantation. All patients remain in complete AV block with a completely paced rhythm at a mean follow-up of 8 +/- 2 months. The McMaster Health Index scores increased from a mean of 0.69 +/- 0.20 before to 0.92 +/- 0.14 after ablation (p = 0.002). The mean Psychological General Well-Being score improved from 59.8 +/- 14.8 at baseline to 84.9 +/- 13.6 6 weeks after discharge (p = 0.001). Treadmill exercise duration increased from 6.4 +/- 4.6 to 9.9 +/- 2.6 minutes (p = 0.03) and correlated strongly with changes in functional capacity measured with the McMaster Health Index (r = 0.70, p = 0.03). These results suggest that catheter ablation of the AV junction and implantation of a rate-adaptive pace-maker significantly improve the quality of life and exercise capacity of patients with paroxysmal AF refractory to medical therapy.

Aged↗