Differential effects of high-frequency versus low-frequency exercise training in rehabilitation of patients with coronary artery disease.

OBJECTIVES: We sought to study the influence of frequency of exercise training during cardiac rehabilitation on functional capacity (i.e., peak oxygen consumption [VO2] and ventilatory anaerobic threshold [VAT]) and quality of life (QoL). BACKGROUND: Although the value of cardiac rehabilitation is now well established, the influence of the different program characteristics on outcome has received little attention, and the effect of frequency of exercise training is unclear. Functional capacity is regularly evaluated by peak VO2 but parameters of submaximal exercise capacity such as VAT should also be considered because submaximal exercise capacity is especially important in daily living. METHODS: Patients with coronary artery disease (n = 130, 114 men; mean age 52 +/- 9 years) were randomized to either a high- or low-frequency program of six weeks (10 or 2 exercise sessions per week of 2 h, respectively). Functional capacity and QoL were assessed before and after cardiac rehabilitation. Global costs were also compared. RESULTS: Compared with baseline, mean exercise capacity increased in both programs: for high- and low-frequency, respectively: peak VO2 = 15% and 12%, Wmax = 18% and 12%, VAT = 35% and 12% (all p < 0.001). However, when the programs were compared, only VAT increased significantly more during the high-frequency program (p = 0.002). During the high-frequency program, QoL increased slightly more, and more individuals improved in subjective physical functioning (p = 0.014). We observed superiority of the high-frequency program, especially in younger patients. Mean costs were estimated at 4,455 and 2,273 Euro, respectively, for the high- and low-frequency programs. CONCLUSIONS: High-frequency exercise training is more effective in terms of VAT and QoL, but peak VO2 improves equally in both programs. Younger patients seem to benefit more from the high-frequency training.

Training effects on peak VO2, specific of the mode of movement, in rehabilitation of patients with coronary artery disease.

Training effects on peak oxygen consumption (VO2), specific to the mode of movement, are well-known in exercise training of young, healthy adults. However, these specific training effects were never studied in patients with coronary artery disease, but may be important in the evaluation of training effects of cardiac rehabilitation programs. Exercise training programs dominated by, for example, cycling might improve peak VO2, measured during cycling, more than during treadmill testing. Therefore, the effects of an exercise training program dominated by cycling and of a program with both cycling and walking/jogging during a 6-weeks cardiac rehabilitation program were evaluated on both cycle ergometer and treadmill. Male patients (aged between 35 and 70 years) with coronary artery disease (history of myocardial infarction and/or angina pectoris and/or coronary artery bypass surgery) were randomly assigned to either a program dominated by cycling (Group I: n=18,mean age 53+/-6.7) or a program with both cycling and jogging (Group II: n=20, mean age 48+/-9.1). Before and after the program peak VO2 was measured on both cycle ergometer and treadmill. At baseline peak VO2 on treadmill was significantly greater than on cycle ergometer in both groups. Peak VO2 (both cycle and treadmill) increased highly significantly during both programs; in group I the increase of peak VO2 on cycle ergometer was greater than on treadmill (respectively, 28.1% versus 18.8%; p<0.05), in contrast to group II (respectively, 22.8% and 16.6%; n.s.). As a result, the difference between peak VO2 on treadmill and cycle ergometer decreased significantly more during the program in group I (p<0.05). These results suggest specific training effects in patients with coronary artery disease and should be considered outcome assessment and exercise prescription of cardiac rehabilitation programs.

Angiographic left ventricular wall motion score to predict arrhythmia recurrence in patients with sustained ventricular tachycardia or fibrillation.

METHODS: Sixty-nine patients with sustained ventricular tachyarrhythmias were followed up to evaluate the predictive value of functional capacity (i.e., New York Heart Association class and peak oxygen consumption) and resting left ventricular function (i.e. radionuclide left ventricular ejection fraction, angiographic left ventricular wall motion score and echocardiographic dimensions) with respect to arrhythmia recurrence. RESULTS: During a mean follow-up of 19 months 18 patients (26%) had an arrhythmia recurrence. Parameters of functional capacity and echocardiographic dimensions were not related to arrhythmia recurrence. Left ventricular ejection fraction and wall motion score were worse in patients with a recurrence compared with the arrhythmia-free patients: 30 +/- 16% versus 40 +/- 19% (mean +/- SD, P = 0.035) and 25 +/- 7 versus 20 +/- 7 (P = 0.01), respectively. Multivariately the most powerful parameter was left ventricular wall motion score (odds ratio 1.12, 95% Cl 1.02-1.23). CONCLUSIONS: Arrhythmia recurrence in ventricular tachyarrhythmia patients relates to resting left ventricular function and not to functional capacity. Since angiographic left ventricular wall motion score is prognostically more important than ejection fraction this parameter should be considered for risk stratification in these patients.

Long-term effect of cardioversion on peak oxygen consumption in chronic atrial fibrillation. A 2-year follow-up.

Restoration of sinus rhythm may improve functional capacity in atrial fibrillation in the short-term. Little is known, however, about its long-term effect on functional status. The aim of the present study was to evaluate the long-term effect of cardioversion on peak oxygen consumption (VO2) in patients with chronic atrial fibrillation. Patients with such a condition and due to undergo electrical cardioversion were eligible for the study. Patients underwent treadmill exercise testing with measurement of peak VO2 before cardioversion, and at 1 month and 2 years thereafter. Based on the rhythm present at those times after cardioversion, patients were categorized into three groups: those in sinus rhythm after 1 month and 2 years (Group I); those in sinus rhythm after 1 month, but with atrial fibrillation after 2 years (Group II); and those who were in atrial fibrillation both at 1 month and 2 years following cardioversion (Group III). Thirty-nine patients were included, and underlying heart disease was present in 24 of them (62%). In the comparison of the baseline characteristics of Group I (n = 17), Group II (n = 11), and Group III (n = 11), underlying heart disease was more frequent in Group I (88%, 45%, and 36%, respectively); otherwise they were similar. In Group I, peak VO2 showed an insignificant increase from 21.1 +/- 5.0 to 22.3 +/- 5.0 ml.min-1.kg-1 month after. cardioversion. After 2 years of sinus rhythm, peak VO2 showed a further increase to 23.8 +/- 5.0 ml.min-1.kg-1 (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Functional capacity before and after cardioversion of atrial fibrillation: a controlled study.

OBJECTIVE: To evaluate the effect of cardioversion on peak oxygen consumption (peak VO2) in patients with long-standing atrial fibrillation, to assess the importance of underlying heart disease with respect to the response to exercise, and to relate functional capacity to long-term arrhythmia outcome. DESIGN: Prospective controlled clinical trial. SETTING: Tertiary referral centre. PATIENTS: 63 consecutive patients with chronic atrial fibrillation accepted for treatment with electrical cardioversion. Before cardioversion all patients were treated with digoxin, verapamil, or a combination of both to attain a resting heart rate < or = 100 beats per minute. INTERVENTIONS: Electrical cardioversion. MAIN OUTCOME MEASURES: Peak VO2 measured before and 1 month after electrical cardioversion to compare patients who were in sinus rhythm and those in atrial fibrillation at these times. Maintenance of sinus rhythm for a mean follow up of 19 (7) months. RESULTS: Mean (1SD) peak VO2 in patients in sinus rhythm after 1 month (n = 37) increased from 21.4 (5.8) to 23.7 (6.4) ml/min/kg (+11%, P < 0.05), whereas in patients with a recurrence of atrial fibrillation 1 month after cardioversion (n = 26) peak VO2 was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to functional capacity or left ventricular function before cardioversion. Baseline peak VO2 was not a predictive factor for long-term arrhythmia outcome. CONCLUSION: Restoration of sinus rhythm improved peak VO2 in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak VO2 was not a predictive factor for long-term arrhythmia outcome after cardioversion of atrial fibrillation. These findings suggest that cardioversion is the best method of improving functional capacity in patients with atrial fibrillation, whether or not they have underlying heart disease and whatever their functional state.

Time course of hemodynamic changes and improvement of exercise tolerance after cardioversion of chronic atrial fibrillation unassociated with cardiac valve disease.

This study prospectively assessed the time course, magnitude and mechanism of the hemodynamic changes after restoration of sinus rhythm in patients with chronic atrial fibrillation (AF) unassociated with valvular disease. Severe cardiac dysfunction may occur after chronic supraventricular tachycardia in patients with and without underlying cardiac disease. Improvement may follow abolishment of the arrhythmia or adequate slowing of the ventricular rate. Eight patients were studied with a mean previous duration of AF of 10 +/- 9 months. Ejection fraction, exercise capacity and the atrial contribution to the left ventricular filling (only during sinus rhythm) were studied before cardioversion, after cardioversion and 1 week, 1 month and 6 months thereafter. A significant improvement in ejection fraction from 36 +/- 13 to 53 +/- 8% (p < 0.05) occurred at 1 month after cardioversion. Concomitantly, peak oxygen consumption had increased at 1 month, from 20.1 +/- 7 to 25.2 +/- 6 ml/min/kg (p < 0.05). Thereafter, no further improvement in hemodynamic parameters occurred. The atrial systole improved already at 1 week (from 3 +/- 5 to 16 +/- 11%, p < 0.05) and remained unchanged thereafter. Thus, restoration of sinus rhythm was associated with a delayed improvement in ejection fraction and maximal exercise capacity, preceded by an early restoration of atrial contractility and an acute slowing of the heart rate. The discrepancy in time course of restoration of atrial and ventricular function parameters suggests that an intrinsic left ventricular cardiomyopathy is present in patients with AF.

Comparison between New York Heart Association classification and peak oxygen consumption in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy.

To compare the value of the New York Heart Association (NYHA) classification and measurement of peak oxygen consumption (VO2) in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure (CHF), 94 patients with clinically stable NYHA class II and III CHF were prospectively studied. In all patients, left ventricular ejection fraction was less than or equal to 40% (mean 22 +/- 9); 49 patients were in NYHA class II, and 45 were in NYHA class III. Mean peak VO2 was 17 +/- 5 ml/min/kg. During a follow-up period of 23 +/- 11 months, 21 patients died. The 1-, 2- and 3-year cumulative survival rates for the 94 patients were 88, 79 and 69%, respectively. Functional status, as assessed both by peak VO2 and NYHA classification, and left ventricular ejection fraction were significantly worse in the group of nonsurvivors. The most powerful independent predictor of mortality was peak VO2. Although mean peak VO2 was significantly higher in NYHA class II than in NYHA class III (20 +/- 4 vs 13 +/- 3 ml/min/kg, p less than 0.0001), categorization into subgroups on the basis of the attained peak VO2 revealed a marked discrepancy with the NYHA classification. Nevertheless, the survival curves of patients subdivided at a peak VO2 of 16 ml/min/kg showed a strong resemblance with survival curves of both NYHA classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional abnormalities of the conduction system in children with an atrial septal defect.

We performed an electrophysiologic study in 40 children with an atrial septal defect and analyzed their pre- and postoperative electrocardiograms and 24-hour Holter recordings. The electrophysiologic study showed a prolonged corrected sinus node recovery time in 83% and an abnormal sinuatrial conduction time in 25% of the children. An early Wenckebach response to atrial pacing was seen in 18%. Sixteen percent had a prolonged atrial conduction time. The atrial functional refractory period was abnormal in 35%. Two children developed nonsustained supraventricular tachycardia during the electrophysiologic study. The preoperative electrocardiogram showed first-degree atrioventricular block in 15% of the children; prolonged periods of accelerated atrial rhythm were found in 35% of the preoperative 24-hour Holter recordings. The incidence of first-degree atrioventricular block and accelerated atrial rhythm decreased postoperatively. We could not find a significant correlation between age or shunt size and the presence of electrophysiologic abnormalities or arrhythmias. These results indicate that the sinus node, atrioventricular node and atrial myocardium show some degree of dysfunction in patients with an atrial septal defect. An early operation may prevent further progression of electrophysiologic abnormalities and the development of symptomatic arrhythmias.

Percutaneous transluminal balloon angioplasty in restenosis of coarctation of the aorta.

Percutaneous transluminal balloon angioplasty was performed in five children with coarctation restenosis. After angioplasty the pressure gradient had decreased considerably in four patients. In all patients aortography showed an increase in the diameter of the lumen at the site of the restenosis. All patients were normotensive the day after angioplasty. There were no complications during or after the procedure.

Hemodynamic effects of dynamic exercise in children and adolescents with moderate-to-small ventricular septal defects.

We studied the hemodynamic effects of dynamic exercise during cardiac catheterization in 35 children and adolescents with small-to-moderate ventricular septal defects. Eighteen of them exercised at 25% and 50% of their maximum workload and 17 exercised at 60%. There was no significant difference between the two groups with respect to age and body mass, height, and surface area. The changes evoked by exercise showed the same pattern at the different workloads, although they were more marked at the higher than at the lower percentage of maximum workload. During exercise the pulmonary vascular resistance did not change, in contrast to the systemic vascular resistance, which decreased. The pulmonary and systemic blood flows both increased, while the left-to-right shunt flow did not change, which led to a decrease of the left-to-right shunt fraction. As the heart rate increased and the shunt flow did not change, the shunt volume per beat decreased during exercise. We conclude that in patients with small-to-moderate ventricular septal defects the hemodynamic effects of dynamic exercise are favorable because the normal rise in systemic blood flow occurs without a corresponding increase in left-to-right shunt flow. Consequently, children and adolescents with such defects should not be restricted in their dynamic exercise activities.

A fiberoptic reflection densitometer with cardiac output calculator.

A catheter-tip densitometer for indocyanine green is described consisting of a cardiac catheter containing optical fibers, an incandescent light source, a light detection unit and a processing unit. Half of the optical fibers guide the light to the blood at the tip of the catheter, the other half the back-scattered (reflected) light to the detection unit. In the detection unit the light is measured by two silicium barrier layer photocells after it has been split into two beams by a beam splitter. In the measuring channel the light passes an 800 nm filter before reaching the photocell. When fiberoptic catheters with glass fibers are employed, the other channel, used for compensation of non-specific effects such as blood flow variations, contains no filter, thus measuring light in a broad spectral band. It is shown that in this way compensation of flow effects may be about two times better than when a 920 nm filter is used. When using plastic optical fibers a 950 nm filter must be used, because above lambda = 850 nm plastic fibers transmit only a band around that wavelength (950 nm). At zero dye concentration the densitometer output or ratio of compensating and measuring photocell output R/R800 is almost insensitive to changes in haemoglobin concentration. When the blood contains dye, however, the influence of haemoglobin concentration is considerable. The densitometer output R/R800 is linearly related to dye concentration up to 50 mg . 1-1, the output R920/R800 up to 30 mg . 1(-1). The output R/R800 decreases with decreasing oxygen saturation; the slope of the calibration line, however, appears to be unaffected. The processing unit also contains an analog cardiac output calculator consisting of an integrator and a divider. Central dye dilution curves recorded from the pulmonary artery after injection of dye into the right atrium or a caval vein come down to the baseline. At this moment the reading of a digital voltmeter displaying the divider output calibrated in 1 . min-1 can be held and the reading taken.

A fiberoptic reflection oximeter.

A catheter tip oximeter is described consisting of a cardiac catheter containing optical fibers, and incandescent light source, a light detection unit and a processing unit. Half of the optical fibers guide the light to the blood at the tip of the catheter, the other half the backscattered (reflected) light to the detection unit. The detection unit contains a dichroic mirror, transmitting most of the light with lambda less than 800 nm and reflecting most of the light with lambda greater than 900 nm, thus splitting the light into two beams. These pass through interference filters with nominal wavelengths of 640 and 920 nm respectively, and are focused on silicium barrier layer photocells. The photocell signals are amplified and fed into a divider giving the ratio of measuring (R640) and compensating (R920) photocell output. The relationship between log R640/R920 and oxygen saturation is represented by a slightly curved line. The relation may be linearized by subtracting a constant voltage from the divided output before taking the logarithm. The slope of the calibration line is dependent on the total haemoglobin concentration. Nonetheless an average calibration line can be used between 70 and 100% oxygen saturation. For 78 measurements of pig blood samples in this range (haemoglobin concentration between 96 and 161 g.1(-1)), the standard deviation of the difference between the fiberoptic oximeter and a Radiometer OSM1 oxygen saturation meter was 1.9% saturation, for 152 samples over the entire saturation range the standard deviation of the difference was 3.1% saturation. The influence of the flow velocity of blood on the light reflection depends on wavelength as well as on oxygen saturation. Therefore, complete compensation for the flow effect is not possible by simple means.

Light-absorbing properties, stability, and spectral stabilization of indocyanine green.

The absorption spectrum of indocyanine green depends on the nature of the solvent medium and on the dye concentration. Binding to plasma proteins causes the principal peaks in the absorption spectrum to shift about 25 nm toward the higher wavelengths. The much greater influence on the spectrum of the dye concentration results from progressive aggregate formation with increasing concentration. Indocyanine green solutions therefore do not follow Lambert-Beer's law above 15 mg-I-1 (in plasma). Indocyanine green solutions in plasma and concentrated (1,000 mg-I-1) solutions in distilled water are stable for at least 4 h. In long-term experiments the optical density of indocyanine green solutions in plasma as well as in distilled water generally diminishes, even in the dark. On the 7th day a new absorption maximum starts to appear at gamma=900 nm, possibly caused by further aggregate formation leading to much larger particles. Spectral stabilization after injection of a concentrated solution into the blood is most rapid when the dye is dissolved in distilled water. Spectral stabilization slows down with decreasing temperature. As rapid spectral stabilization is essential in quantitative dye dilution studies, the practice of adding a albumin and/or isotonic saline solution to the injectate should be discontinued. When a 10 g-1(-1) aqueous solution of indocyanine green is used, spectral stabilization takes less than 1.5 a (at 37 degrees C), which is sufficiently fast for almost any application.