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HEMODYNAMIC RESPONSE TO EXERCISE IN A RIGHT VENTRICULAR IMPEDANCE SENSOR DRIVEN PACEMAKER

L. Cook; D. Hamilton; E. Busse; J. Tsang; W. Wojack; G. Garbe; R. Haennel; University of Regina and Regina Health District, Regina, SK

 

This study examined the effects of a closed loop (CLS) right ventricular impedance (RVI) sensor on exercise hemodynamics. Twelve patients (7 men, 5 women; age 70.5 +/- 3 years), implanted with the INOS2+ pacemaker 4 to 6 weeks earlier, participated in this study. All patients completed two graded exercise tests, using the Chronotropic Assessment Exercise Protocol (CAEP) to symptom-limited fatigue. For both tests, the pacemaker was programmed into DDD-CLS mode, with an upper rate limit of 75% to 85% of age predicted maximum heart rate (HR) and a lower rate of 60 beats/min. The AV delay was tailored to each patient to ensure 100% ventricular pacing. Heart rate was recorded using a continuous lead II ECG (GEMS(TM) software, CardioComm Solutions). An average of 5 beats in the last 10 seconds of each stage was used in the analysis. The pacing rate was reported as a percentage of the programmed maximum CLS rate. Oxygen uptake (VO2) was measured by the TrueMax 2400 system (Parvo Medics). The average of the last minute of each stage was used in the analysis. Stroke volume (SV) and cardiac output (QC) were determined using Impedance Cardiography (Surcom Inc.) measured in the last minute of each stage. The test-retest reliability of HR and QC responses to graded exercise was analyzed using analysis of variance of repeated measures. There were no significant differences in HR (P = .654, F = .212) or QC (P = .871, F = .027) response between tests for each patient. The test-retest reliability coefficient of the HR response is r = .99 (P < .01). Furthermore, there were significant correlations (P < .01) between both VO2 to HR and VO2 to QC with regression coefficients of [beta] = .598 and [beta] = .529, respectively. The CLS RVI sensor driven pacemaker produced reliable and positive hemodynamic responses to graded exercise on a test-retest basis.

 

EFFECTS OF BETA-BLOCKER ON MAXIMAL HEART RATE AND RATE PRESSURE PRODUCT DURING MORNING AND AFTERNOON EXERCISE STRESS TEST IN CORONARY HEART DISEASE PATIENTS

Monique H. Dufour*+; Pierre Boulay+; Denis Prud'homme++; *Division of Kinesiology, Department of Social and Preventive Medicine, Laval University, Ste-Foy, Quebec; +School of Kinesiology and Recreology, University of Moncton, Moncton, NB; ++School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario

 

The purpose of this study was to investigate the variation in maximal heart rate (HRmax) and rate pressure product (RPP) during morning and afternoon exercise stress test in coronary heart disease (CHD) patients treated with a beta-blocker. Eighteen CHD patients (7 women, 11 men) aged 59.8 +/- 9.3 years (mean +/- SD) who were part of a cardiac rehabilitation program participated in this study. There were 10 patients treated with metoprolol (100 +/- 33 mg twice daily) and 8 patients treated with atenolol (75 +/- 35 mg daily). After four visits of exercise familiarization, all the subjects underwent, on two different days, a morning and an afternoon indirect maximal exercise stress test (Bruce protocol) 2 to 3 hours (am) and 8 to 10 hours (pm) after their medication intake. The time of day in which the subjects did their maximal exercise stress tests was randomly assigned. During the tests, a 12-lead ECG was read continuously. Heart rate (HR), blood pressure (BP), rate of perceived exertion (RPE), and RPP were measured at the end of each stage, and at maximal exercise. No significant differences in exercise capacity (8.4 +/- 1.8 vs 8.4 +/- 1.7 METs;P < .01) and RPE (7.2 +/- 1.3 vs 7.6 +/- 1.5;P < .01) were observed between the two (afternoon and morning) stress tests. However, HRmax (126 +/- 22 vs 111 +/- 19 bpm;P < .01) and RPP (207.5 +/- 62.0 vs 163.8 +/- 47.1 mm Hg x bpm x 10-2;P < 0.01) were 13.5% and 26.8% higher in the afternoon than the morning stress test, respectively. No patients experienced angina and there were no ischemic signs on the ECG during morning exercise stress tests. However, 5 of the 18 patients (28%) demonstrated significant ST-segment depression (>= 1.0 mm of horizontal or downsloping) and 3 of them experienced angina during afternoon exercise stress test. The results of this study suggest that there is considerable diurnal variation in hemodynamic response to a maximal exercise test. Such variation in HR may have important clinical implications when exercise testing is used to determine exercise training HR. Thus, the time of day of maximal exercise testing should be taken into consideration for the exercise prescription of patients with a beta-blocker.

 

FIRST YEAR RESULTS OF THE EXTENSIVE LIFESTYLE MANAGEMENT INTERVENTION (ELMI) FOLLOWING CARDIAC REHABILITATION TRIAL

Scott A. Lear; Andrew Ignaszewski; Wolfgang Linden; Anka Brozic; Marla Kiess; John J. Spinelli; P. Haydn Pritchard; Jiri J. Frohlich; University of British Columbia, Vancouver, BC, Canada

 

Previous reports have indicated that lifestyle adherence declines and risk factors worsen following a cardiac rehabilitation program (CRP). To address this issue we conducted a 4-year ELMI in graduates of a CRP and present the results of the first year.

 

Methods:

A total of 302 men and women with ischemic heart disease were recruited following completion of two local CRP and randomized to an ELMI or Usual Care (UC) group. The ELMI was case-managed and consisted of 6 supervised exercise sessions, 6 telephone follow-up calls and 2 risk factor and lifestyle management sessions. Current clinical guidelines were followed and pharmacological management was carried out via recommendations to the family physician. The UC group returned after 1 year for outcome assessment. The primary outcome was global cardiovascular risk determined by the Framingham and Procam risk scores with secondary outcomes of the component risk factors.

 

Results:

Baseline data was similar between the two groups. Outcome data were available for 142 ELMI and 136 UC participants. Adherence to the ELMI was high: exercise sessions 83%, telephone calls 90%, and counselling sessions 94%. After an average follow-up of 13 months, there was a nonsignificant trend in favor of the ELMI with respect to change in the Framingham (6.6 +/- 3.1 to 6.2 +/- 2.9 vs 6.6 +/- 3.2 to 6.7 +/- 3.2, P =.138) and the Procam (20.0 +/- 20.0 to 20.6 +/- 19.5 vs 19.1 +/- 18.7 to 21.8 +/- 19.1, P = .089) scores. For the UC group, the Procam score was significantly worse compared to baseline. There were no significant differences between the groups for the secondary outcomes.

 

Conclusions:

These results indicate that a modest post-CRP intervention provides no significant benefit beyond current usual care practices.

 

A COMPARISON OF MEASURED AND PREDICTED QT INTERVALS IN PACED PATIENTS DURING EXERCISE

C. Tomczak*; E. Busse+; A. Simon++; A. Klesius++; U. Abdel-Rahman++; B. Grasser[S]; F. Iberer[S]; R. G. Haennel*; *Cardiovascular Research Unit, Faculty of Kinesiology and Health Studies, University of Regina, Regina, Saskatchewan; +Division of Cardiovascular Surgery, Regina General Hospital, Regina, Saskatchewan; ++Johann-Wolfgang-Goethe University, Frankfurt, Germany; [S]University Hospital, Graz, Austria

 

Purpose:

The purpose of this study was to compare intracardial evoked QT intervals with QT interval values obtained using the prediction equation for ACSM's normal QT intervals for a given RR interval.

 

Methods:

Nineteen patients (10 female and 9 male; ages 23-87, mean 63.3 +/- 18.0) with an ejection fraction (EF), > 40% (mean EF = 60.9% +/- 8.0) were included in this study. All patients were previously implanted with the Diamond II (Vitatron) pacemaker and were screened for postimplant myocardial infarctions, chronic atrial fibrillation and flutter, and ongoing ischemia. The pacemaker was set in DDDR mode during a graded exercise test (modified Chronotropic Assessment Exercise Protocol [CAEP]) and intracardial evoked QT intervals were measured continuously for each RR interval using customized software developed by the manufacturer. The predicted QT for a given RR was derived using a formula from Simonson et al where predicted QT = 0.2423 +/- 0.140 * RR + 0.0003 * age. The predicted QT values obtained from the equation were then compared to the intracardial evoked QT intervals for the same measured RR intervals.

 

Results:

The average measured intracardial evoked QT interval was reported to be 306 ms +/- 35 while the average predicted QT interval was reported to be 359 ms +/- 29. Using Pearson's product-moment correlation, the regression between recorded RR intervals and intracardial evoked QT intervals, as measured by the Diamond II pacemaker, was found to be significant (P < .01) with an R2 of .591 and a standardized regression coefficient of [beta] = 0.768. The association between the predicted QT intervals for the same RR intervals was found to be significant (P < .01) with an R2 of .961 and a standardized regression coefficient of [beta] = 0.980. A comparison for difference between the regression coefficients for measured versus predicted RR-QT demonstrated a significant difference (P < .001) between these two slopes.

 

Conclusion:

The results indicate that the predicted QT intervals for a given age and heart rate, for the patients in this study, are significantly higher than the QT intervals measured by the Diamond II pacemaker. The results of this study also raise the possibility that the ACSM's normal QT interval values for a given heart rate may need to be re-examined.

 

PARTICIPANT ADHERENCE TO INTENSIVE VERSUS DISTRIBUTED EXERCISE-BASED CARDIAC REHABILITATION INTERVENTIONS

Louise Beaton; Sophia Papadakis; Robert Reid; Louise Morrin; William Dafoe; Ottawa Heart Institute

 

Exercise-based cardiac rehabilitation programs (CRPs) have well-established benefits on patient mortality, cardiac risk profiles, and health-related quality of life. Patient adherence to exercise-based CRPs plays a key role in determining the extent to which benefits are derived. To date, it has not been determined how best to structure CRPs in order to promote patient adherence.

 

Objective:

To compare exercise session adherence rates between an intensive 3-month versus a distributed 12-month program of cardiac rehabilitation.

 

Methods:

392 patients with CAD were randomized to a 3-month (33-session) or 12-month (33-session) multifactorial CRP. Both intervention groups received the same number of exercise sessions (27). The 3-month intensive program consisted of twice weekly exercise sessions over 14-weeks.

 

The 12-month program was distributed in three progressively tapered blocks of weekly (1-3 months), bi-monthly (3-6 months), and monthly (6-12 months) exercise sessions. Adherence rates between the two program lengths of CRP were compared by 2-tailed independent t tests and between frequency blocks by one-way ANOVA.

 

Results:

Regardless of CRP length the percentage of exercise sessions attended did not significantly differ between groups (3-month: 78.3% +/- 29.7%; 12-month: 75.7% +/- 29.6%). The distribution of exercise sessions was found however, to impact on adherence rates. Within the 12-month CRP a significant reduction (20.3%, P = .00) in adherence was observed when exercise frequency was reduced from bimonthly to monthly sessions.

 

Conclusions:

Patient adherence to exercise sessions is not affected by CRP length. Exercise session distribution, however, does appear to influence adherence, particularly when the distribution is reduced to monthly exercise sessions. These findings have important implications for the design of efficacious and cost-effective CRPs. Further evaluation is required to determine the optimal distribution of exercise sessions required to encourage patient adherence and improve health outcomes.

 

FIGURE

  
Figure. Adherence ra... - Click to enlarge in new windowFigure. Adherence rates of the 3-month and 12-month CRPs.

IMPACT OF CARDIAC REHABILITATION PROGRAM LENGTH ON PSYCHOLOGICAL DISTRESS AND HEALTH-RELATED QUALITY OF LIFE

Robert Reid; William Dafoe; Neil Oldridge; Louise Morrin; Alain Mayhew; Sophia Papadakis; Louise Beaton; Ottawa Heart Institute, Ottawa, Ontario

 

Cardiac rehabilitation programs (CRP) are known to have beneficial effects on indicators of psychological distress and health-related quality of life. Optimum program length, however, has not been determined.

 

Purpose:

This study compared the efficacy of an intensive (3-month, 33-session) versus a distributed (12-month, 33-session) CRP as measured by changes in psychological distress and health-related quality of life.

 

Methods:

388 patients with CAD (mean age 57.9 +/- 10.9 years, 84.1% male) were randomly assigned to either an intensive (n = 196) or a distributed (n = 192) multifactorial CRP. The 3-month group attended twice weekly and the 12-month group once a week for 14 weeks, once every 2 weeks for 14 weeks, and once a month for 24 weeks. Outcomes measured at baseline and at 13, 26, and 52 weeks included changes in perceived stress (Perceived Stress Scale), depressive symptoms (Centre for Epidemiological Studies-Depression), disease-specific quality of life (MacNew Quality of Life After MI), and generic health-related quality of life (SF-36). For the primary analysis, change scores between baseline and 52 weeks were compared using independent t tests.

 

Results:

Results are shown in the Table : mean +/- SD for changes in measures of psychological distress and quality of life.

  
Table. No caption av... - Click to enlarge in new windowTable. No caption available.*

Conclusions:

One year following program intake, participants assigned to a 12-month program of CRP demonstrated greater improvement in the mental health domain of generic health-related quality of life. There were no differences for perceived stress, depressive symptoms, or disease-specific quality of life.

 

IMPACT OF PROGRAM LENGTH ON FUNCTIONAL CAPACITY AND PHYSICAL ACTIVITY LEVELS

Louise Morrin; Alain Mayhew; Robert Reid; Sophia Papadakis; Louise Beaton; William Dafoe; University of Ottawa Heart Institute, Ottawa, ON

 

The optimal cardiac rehabilitation program (CRP) length to establish new lifestyle patterns such as regular physical activity is unknown.

 

Purpose:

To compare the efficacy of a 3-month versus a 12-month CRP, as measured by changes in physical activity parameters and functional capacity.

 

Method:

392 consenting patients with CAD (mean age 57.9 +/- 10.9 years, 84.1% male) referred to a CRP were randomized to an intensive (3-month, 33-session, n = 197) or a distributed (12-month, 33-session, n = 195) multifactorial CRP. The 3-month group attended twice weekly, and the 12-month group once a week for 14 weeks, once every 2 weeks for 14 weeks, and once a month for 24 weeks. Variables were assessed at baseline, 3, 6, and 12 months, and included direct-measured peak oxygen uptake (METs), Caltrac accelerometer-measured activity (kcal/day), and self-reported physical activity (kcal/day) measured by a 7-day physical activity recall (PAR) interview. Baseline characteristics and change scores at 1 year from program intake (12 months minus baseline values) were compared using two-tailed independent t tests with program-length assignment as the grouping factor.

 

Results:

There were no baseline differences between the groups. There were no significant differences between the groups in changes from baseline to 12 months in any measures. See Table : mean +/- SD of baseline, 12 months, and change between baseline and 12-month variables.

  
Table. No caption av... - Click to enlarge in new windowTable. No caption available.*

Conclusion:

One year after program intake, there was no difference in the efficacy of a 3-month versus a 12-month CRP in improving functional capacity or regular physical activity. Extending program length an additional 9 months, without increasing the number of contacts, did not result in more effective adoption of regular physical activity or greater improvement in exercise tolerance at 1 year.