Peak Exercise Oxygen Consumption Research Articles

Cardiac cycle-dependent changes in aortic area and distensibility are reduced in older patients with isolated diastolic heart failure and correlate with exercise intolerance

OBJECTIVESThe goal of this study was to determine if cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility are associated with exercise intolerance in elderly patients with diastolic heart failure (DHF).BACKGROUNDAortic compliance declines substantially with age. We hypothesized that a reduction in cardiac cycle-dependent changes in thoracic aortic area and distensibility (above that which occurs with aging) could be associated with the exercise intolerance that is prominent in elderly diastolic heart failure patients.METHODSThirty subjects (20 healthy individuals [10 < 30 years of age and 10 > 60 years of age] and 10 individuals > the age of 60 years with DHF) underwent a magnetic resonance imaging (MRI) study of the heart and proximal thoracic aorta followed within 48 h by maximal exercise ergometry with expired gas analysis.RESULTSThe patients with DHF had higher resting brachial pulse and systolic blood pressure, left ventricular mass, aortic wall thickness and mean aortic flow velocity, and, compared with healthy older subjects, they had a significant reduction in MRI-assessed cardiac cycle-dependent change in aortic area and distensibility (p < 0.0001) that correlated with diminished peak exercise oxygen consumption (r = 0.79). After controlling for age and gender in a multivariate analysis, thoracic aortic distensibility was a significant predictor of peak exercise oxygen consumption (p < 0.04).CONCLUSIONSOlder patients with isolated DHF have reduced cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility (beyond that which occurs with normal aging), and this correlates with and may contribute to their severe exercise intolerance.

Cardiac Transplantation 40 Years After a Stab Wound to the Heart

Cardiac Transplantation 40 Years After a Stab Wound to the Heart

Dobutamine-induced augmentation of left ventricular ejection fraction predicts survival of heart failure patients with severe non-ischaemic cardiomyopathy.

The prognosis of patients with severe non-ischaemic dilated cardiomyopathy is variable. The predictive value of currently utilized tests is suboptimal. The purpose of this study was to determine the prognostic value of dobutamine-induced augmentation of left ventricular ejection fraction in patients with non-ischaemic dilated cardiomyopathy. Sixty-two patients with left ventricular ejection fraction < or =0.30 underwent exercise testing with gas exchange analysis and assessment of left ventricular ejection fraction at rest and after a 10-min intravenous infusion of dobutamine at 10 microg x kg(-1) x min(-1), using equilibrium radionuclide ventriculography. Age was 48+/-11 years, 32% females, functional class 2.6+/-0.6, resting left ventricular ejection fraction 0.20+/-0.06, and peak exercise oxygen consumption (mVO2) 19+/-6 ml x kg(-1) x min(-1). Mean dobutamine-induced augmentation of left ventricular ejection fraction (DeltaLVEF) was 0.09+/-0.06 (median 0.08, range -0.03 to 0.26). Follow-up was 25+/-15 months during which there were 12 deaths and five transplantations. Patients were divided into two groups based on median DeltaLVEF. The transplant-free survival was better in the group with higher DeltaLVEF (94% vs 64%, P<0.008). In multivariate analysis incorporating age, gender, duration of chronic heart failure, functional class, right and left ventricular ejection fraction, DeltaLVEF, left ventricular end-diastolic volume index, and mVO2, only DeltaLVEF was predictive of 1-year, 3-year, and overall transplant-free survival (RR 0.09, 0.03, and 0.13;P 0.03, 0.09, and 0.08 respectively). The linear correlation between DeltaLVEF and mVO2(r=0.3) and between DeltaLVEF and left ventricular ejection fraction (r=0.5) was weak. Dobutamine-induced augmentation of left ventricular ejection fraction is a strong prognostic variable, independent of exercise capacity and resting ventriculographic variables, in severe non-ischaemic systolic dysfunctional heart failure.

Dobutamine echocardiographic study in patients with nonischemic dilated cardiomyopathy and prognostically borderline values of peak exercise oxygen consumption: 18-month follow-up study

OBJECTIVESWe sought to study the prognostic value of dobutamine echocardiography in patients with nonischemic dilated cardiomyopathy (DCM) and prognostically borderline values of peak oxygen consumption (VO2max) during exercise.BACKGROUNDChanges in echocardiographic variables assessed by dobutamine echocardiography can be used to evaluate the functional status of patients with chronic heart failure (CHF) and DCM.METHODSIn 27 consecutive patients (mean age 55 ± 15 years) with VO2max values between 10 and 14 ml/kg body weight per min, a low infusion rate (10 μg/kg per min) dobutamine echocardiographic test was performed. The induced changes in echocardiographic variables were measured, and an 18-month follow-up study was done.RESULTSAt the end of the protocol, 9 patients (group I) had died from cardiac reasons, whereas the remaining 18 patients (group II) survived. After dobutamine infusion, the left ventricular end-systolic diameter (LVESD) was smaller in group II (6.22 ± 0.94 cm) than in group I (6.99 ± 0.76 cm; p < 0.05), whereas end-systolic wall stress (ESWS) was higher in group I (1030.66 ± 193.98 g/cm2) than in group II (691.57 ± 297.06 g/cm2; p < 0.05). The changes in LVESD and ESWS were greater in group I (0.75 ± 0.36 cm and 463.11 ± 159.87 g/cm2, respectively) than in group II (−0.04 ± 0.36 cm and 83.16 ± 291.74 g/cm2, respectively; p < 0.01 for both).CONCLUSIONSIn the “gray” zone of VO2max, dobutamine echocardiography seems to be a valuable prognostic indicator in patients with CHF and DCM.

ALTERATIONS OF MYOCARDIAL BLOOD FLOW IN PATIENTS WITH CARDIOMYOPATHY FOLLOWING LONG-TERM LVAD SUPPORT

Background: Circulatory support with an implantable LVAD has been shown to normalize perfusion pressure, reduce left ventricular (LV) wall stress, and improve LV structure and myocyte function, in some cases enabling LVAD explant. Improvement in myocardial blood flow (MBF) as a consequence of improved hemodynamics may contribute to the subsequent beneficial changes observed in myocyte structure and function following long-term LVAD implant. Methods: Positron emission tomography (PET) with [13N]ammonia imaging was performed in 5 patients with cardiomyopathy (all male, median age 57, 2 ischemic, 3 idiopathic) at the time of evaluation for LVAD implant (HeartMate® LVAD; Thermo Cardiosystems, Inc) and subsequently at 4–6 weeks following implant. In three of the patients, pre and postoperative hemodynamic and exercise testing were available. Results: Following LVAD implant, there was a significant improvement in hemodynamics and peak exercise oxygen consumption (mean improvements in cardiac index 3.5 vs. 1.8 1/min/m2, pulmonary capillary wedge pressure 9 vs. 25 mm Hg, maximum exercise oxygen consumption 17 vs. 13 ml/kg/min, p<.05 for each). In 3 of 5 patients, MBF increased an average of 101%. 2 patients demonstrated no change in MBF. Conclusions: Despite restoration of normal hemodynamics with significant LV unloading, these data suggest that alterations in MBF are variable and may be related to coronary autoregulation and myocardial oxygen demand. These data have implications for potential LV recovery following long-term LVAD support.

Relationship between peak exercise oxygen consumption and QTC in patients with advanced heart failure

Relationship between peak exercise oxygen consumption and QTC in patients with advanced heart failure

Congestive heart failure treatment: the pacing approach.

Early reports of physiologic pacing for congestive heart failure (CHF) yielded conflicting results, and little enthusiasm was generated for pacing as a mode of therapy for CHF. Small, uncontrolled studies, which had little or no follow-up demonstrated that pacing from the left ventricle could synchronize contraction of the ventricles and improve overall ventricular performance. These encouraging reports led to a number of larger, multicenter trials, which have been recently reported. These trials have consistently shown improvements in such objective measurements as peak exercise oxygen consumption, ejection fraction, heart rate variability, 6-minute walk test distance and anaerobic threshold, as well as subjective improvements such as quality of life assessment. A number of large, multicenter double-blinded trials are ongoing which will seek to further assess the benefits of biventricular or multisite pacing. Among the important issues, which will be addressed by ongoing trials, are the possibility of pacing induced arrhythmias, the benefit of adding defibrillator capability to these pacing systems, and the development of novel delivery systems, which will make implantation of these systems more accessible to clinicians. Studies to date have largely excluded patients with traditional indications for pacing, and have been confined chiefly to patients with PR interval prolongation, and left bundle branch block with a QRS duration greater than 120 milliseconds, with New York Heart Association class II or III CHF. Whether this therapy will offer benefit to other patients who do not meet these criteria is also unknown at present. Another novel mode of pacing therapy, which may be clinically appropriate for a broader range of CHF patients, is contractility modulation, which involves subthreshold pacing to increase intracellular calcium and enhance inotropy. Early data suggests that the benefits of these two forms of pacing therapy may be additive.

Effects of simulated altitude-induced hypoxia on exercise capacity in patients with chronic heart failure

PURPOSE: Patients with stable heart failure often wish to spend time at altitudes above those of their residence. However, it is not known whether they can safely tolerate ascent to high altitudes or what its effects on work capacity may be. SUBJECTS AND METHODS: We studied 14 normal subjects and 38 patients with clinically stable heart failure, 12 of whom had normal workload [peak exercise oxygen consumption (VO 2) greater than 20 mL/min/kg], 14 of whom had slightly diminished workload (peak VO 2 20 to 15 mL/min/kg), and 12 of whom had markedly diminished workload (peak VO 2 less than 15 mL/min/kg) at baseline. All performed cardiopulmonary exercise tests with inspired oxygen fractions equal to those at 92, 1,000, 1,500, 2,000, and 3,000 m, and maximum achieved work rates (mean ± SD) were measured. RESULTS: All subjects completed the trial; no test was interrupted because of arrhythmia, angina, or ischemia. Maximum work rate decreased in parallel with increasing simulated altitude. The percentage decrease was greater for patients with heart failure and was most marked among those with the lowest workload at baseline. Maximum achieved work rate declined by 3% ± 4% per 1,000 m in normal subjects, by 5% ± 3% ( P <0.01) in patients with heart failure with normal workload, by 5% ± 4% ( P <0.01) in patients with slightly diminished workload, and by 11% ± 5% ( P <0.01 vs normal subjects and vs the other patients with heart failure) in patients with markedly reduced workload. CONCLUSION: Patients with stable heart failure who ascend to higher altitudes should expect to have a reduction in maximum physical activity in proportion to their exercise capacity at sea level.

Low-dose dobutamine responsiveness in idiopathic dilated cardiomyopathy: relation to exercise capacity and clinical outcome.

To evaluate myocardial contractile reserve using low-dose dobutamine echocardiography in patients with chronic heart failure secondary to idiopathic dilated cardiomyopathy stratified by peak exercise oxygen consumption (VO(2)). Sixty clinically stable patients (56+/-11 years; 45 males) with idiopathic cardiomyopathy and NYHA class I to III symptoms of heart failure were studied and followed-up for 13+/-3 months. All patients underwent cardiopulmonary exercise testing and low-dose dobutamine. The dobutamine infusion protocol consisted of an initial dose of 2.5 micro. kg(-1)per 3 min, increasing by 2.5 micro. kg(-1)per min every 3 min; the maximal dose was 10 micro. kg(-1)per min. The end-systolic volume index, left ventricular ejection fraction and cardiac output were measured at baseline and peak dobutamine dose and their change calculated as ((peak dose value-baseline value)/baseline value]x100. Ten normal subjects with normal left ventricular function and no coronary artery lesions served as a control group to compare low-dose dobutamine results. All analysed echocardiographic variables either at baseline or following dobutamine infusion were significantly lower in patients with chronic heart failure as a whole compared to the control group. When the patients were grouped according to Weber's classification, a statistically significant decrease in percentange changes in end-systolic volume index (rho=-0.77;P<0.0001), left ventricular ejection fraction (rho=-0.72;P<0.0001) and cardiac output (rho=-0. 82;P<0.0001) from class A to class C was observed. The mean percentage decrease in end-systolic volume index following the dobutamine infusion was 28.7+/-9% in class A (peak VO(2)>20 ml. kg(-1). min(-1)), 18.6+/-8% in class B (peak VO(2)between 16 and 20 ml. kg. min(-1)), and only 6.4+/-6% in class C (peak VO(2)between 10 and 16 ml. kg(-1). min(-1)) patient groups. At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with a peak VO(2)<15 ml. kg(-1). min(-1)(P=0.006). During the follow-up, 17 patients had events (15 readmissions for worsening heart failure and two deaths). At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with the occurrence of events (P=0.003). The area under the receiver operating characteristic curve for percentage change in end-systolic volume index was not significantly different from that for peak VO(2)(0. 86+/-0.04 vs 0.80+/-0.06;P:ns). This study indicates that in patients with chronic heart failure secondary to idiopathic cardiomyopathy, the cardiac response to low-dose dobutamine, as assessed by echocardiography, is correlated with peak VO(2), an objective and accurate measure of the severity of the disease and clinical outcome.

Predictors of early post-cardiac transplant exercise capacity.

This study was conducted to identify which pre- and perioperative clinical parameters were predictive of predischarge submaximal exercise capacity and early postdischarge maximal exercise capacity in cardiac transplant recipients. We studied 24 patients (mean age = 46; 25% African American) who underwent cardiac transplantation followed by an early (immediately posttransplant) postoperative exercise training program. The patients' submaximal exercise capacity was measured at hospital discharge (25 days posttransplant) using the 6-minute distance walk test. Maximal cardiopulmonary exercise testing was done within 4 months of hospital discharge (68 days) to measure peak exercise oxygen consumption (VO2) and to estimate peak exercise capacity as measured by metabolic equivalents (METs). Six clinical variables were assessed for their relationship with predischarge submaximal exercise capacity and 10 clinical variables were evaluated for their relationship with early posttransplant maximal exercise capacity. Predischarge submaximal exercise capacity was correlated with postdischarge estimated METs (r = 0.43; P = 0.04). No predictors of predischarge submaximal exercise capacity were identified. Predictors of estimated peak exercise METs following discharge were younger age, longer time since resolution of rejection, and shorter postoperative hospitalization. Younger age was the only predictor of peak VO2. Postoperative physical training may improve exercise capacity early after transplantation and minimize effects of preoperative clinical factors that could negatively affect exercise capacity. Interpretation of these results, however, is limited by the small sample and absence of a nonexercising control group. Older recipients, those with a longer length of hospital stay, and shorter duration of time since resolution of rejection may be at risk of reduced early postoperative maximal exercise capacity. Identification of these predictors is important to maximize early reconditioning efforts and plan outpatient rehabilitation.

Impaired pulmonary diffusion during exercise in patients with chronic heart failure.

Pulmonary diffusion is impaired at rest in patients with chronic heart failure (CHF) and has been implicated in the generation of symptoms and exercise intolerance. The aim of this study was to determine whether pulmonary diffusion is impaired during exercise in CHF, to examine its relationship to pulmonary blood flow, and to consider its functional significance in relation to metabolic gas exchange. Carbon monoxide transfer factor (TLCO) and pulmonary blood flow (Q(C)) were measured by a rebreathe technique at rest and during steady-state cycling at 30 W in 24 CHF patients and 10 control subjects. Both patients and control subjects were able to raise TLCO and Q(C) during exercise. However, the patient group had a lower diffusion for a given blood flow (TLCO/Q(C)) both at rest (3.6+/-0.16 and 4.8+/-0.23 mL x L(-1) x mm Hg(-1); P<0.001) and during exercise (2.8+/-0.16 and 3.4+/-0.13 mL x L(-1) x mm Hg(-1) for CHF patients and control subjects, respectively; P<0.05). TLCO/Q(C) was related to the ventilatory equivalent for carbon dioxide (VEVCO(2)) production at 30 W (TLCO/Q(c) versus VEVCO(2), r = -0.58, P<0.01) and to peak exercise oxygen consumption measured during a progressive test (TLCO/Qc versus VO(2peak), r = 0.57, P<0.01) in these patients. Patients with CHF are able to recruit reserves of TLCO and Q(C) during exercise. However, the TLCO/Q(C) ratio is consistently impaired in these patients and relates to both exercise hyperpnea and peak exercise oxygen consumption. Whether this impairment in alveolar gas exchange is reversible in CHF and therefore is a potential target for therapy has yet to be determined.

High prevalence and persistence of sleep apnoea in patients referred for acute left ventricular failure and medically treated over 2 months.

Cardiac failure patients were studied systematically using polysomnography 1 month after recovering from acute pulmonary oedema, and again after 2 months of optimal medical treatment for cardiac failure. This prospective study of consecutive patients was conducted in a cardiac care unit of a university hospital. V o(2)measurements and left ventricular ejection fraction were recorded. Thirty-four patients, initially recruited with pulmonary oedema, improved after 1 month of medical treatment to NYHA II or III. They were aged less than 75 years and had a left ventricular ejection fraction less than 45% at the time of inclusion. Age was 62 (9) years, body mass index= 27 (5) kg x m(-2)and an ejection fraction= 30 (10)%. Eighteen of the 34 patients (53%) had coronary artery disease. Twenty-eight of the 34 had sleep apnoea syndrome with an apnoea+hypopnoea index >15 x h(-1)of sleep. Thus, the prevalence of sleep apnoea in this population was 82%. Twenty-one of 28 (75%) patients had central sleep apnoea and seven of 28 (25%) had obstructive sleep apnoea. Patients with central sleep apnoea had a lower Pa co(2)than those with obstructive sleep apnoea (33 (5) vs 37 (5) mmHg, P<0.005). Significant correlations were found between apnoea+hypopnoea index and peak exercise oxygen consumption (r= -0.73, P<0.01), and apnoea+hypopnoea index and Pa co(2)(r= -0.42, P = 0.03). When only central sleep apnoea patients were considered, a correlation between apnoea+hypopnoea index and left ventricular ejection fraction was also demonstrated (r= -0.46, P<0.04). After 2 months of optimal medical treatment only two patients (both with central sleep apnoea) showed improvement (apnoea+hypopnoea index <15 x h(-1)). We have demonstrated a high prevalence of sleep apnoea, which persisted after 2 months of medical treatment, in patients referred for acute left ventricular failure. Central sleep apnoea can be considered a marker of the severity of congestive heart failure.

Assessment of the functional status of heart failure in non ischemic dilated cardiomyopathy: an echo-dobutamine study.

The functional status of heart failure (HF) is conventionally evaluated by peak exercise oxygen consumption (VO2 max). Dobutamine echocardiography can be used to evaluate myocardial reserve. The aim of this study was to estimate the functional status of chronic HF in patients with dilated cardiomyopathy, by investigating the changes in echo-variables, as assessed by echo-dobutamine, in relation with VO2 max. A low infusion rate echo-dobutamine test (10 micrograms/kg/min) was performed in 30 patients with dilated cardiomyopathy and 1 h later VO2 max was measured. VO2 max (ranging from 7.6 to 23 ml/kg/min, mean 14.06 +/- 0.64 ml/kg/min) was correlated with the changes (values obtained after inotropic stimulation minus those obtained at baseline) in left ventricular end-systolic diameter (r:0.80, p:0.001), in left ventricular end-systolic posterior wall thickness (r:0.73, p:0.001) and in left ventricular heart-rate corrected mean velocity of circumferential fiber shortening (Vcfc)/end-systolic meridional wall stress ratio (r:0.64, p:0.0001). A negative correlation was found between VO2 max and the changes in end-systolic meridional wall stress (r: -0.76, p:0.001). After dobutamine infusion Vcfc/systolic meridional wall stress ratio increased in patients with VO2 max > 14 ml/kg/min but decreased in patients with VO2 max < 14 ml/kg/min (0.0001 +/- 0.0001 vs -0.0002 +/- 0.0003 circ x cm2/g x s, p:0.0001). End-systolic meridional wall stress was decreased in patients with VO2 max > 14 ml/kg/min but increased in patients with VO2 max < 14 ml/kg/min (-126.97 +/- 34.24 vs 205.77 +/- 56.71 g/cm2, p:0.0001). The changes in echo-variables assessed by echo-dobutamine are well correlated with VO2 max and seem to be accurate for evaluating the functional status of chronic HF in patients with dilated cardiomyopathy.

Assessment of functional capacity through oxygen consumption in patients with asymptomatic probable heart disease.

To compare peak exercise oxygen consumption (VO2peak) of healthy individuals with asymptomatic individuals with probable heart disease. Ninety-eight men were evaluated. They were divided into two groups: 1) 39 healthy individuals (group N) with an age range of 50 +/- 4.6 years; and 2) 59 asymptomatic individuals with signs of atherosclerotic and/or hypertensive heart disease (group C) with an age range of 51.9 +/- 10.4 years. In regard to age, height, body surface area, percentage of fat, lean body mass, and daily physical activity, both groups were statistically similar. Environmental conditions during the ergometric test were also controlled. Maximal aerobic power (watts), VO2peak, maximal heart rate, and maximal pulmonary ventilation were lower in group C (p < 0.01) than in group N; weight, however, was lower in group N (p = 0.031) than in group C. Differences in the respiratory gas exchange index, heart rate at rest, and the maximal double product of the two groups were not statistically significant. Signs of probable heart disease, even though asymptomatic, may reduce the functional capacity, perhaps due to the lower maximal cardiac output and/or muscle metabolic changes.

The influence of diastolic and systolic function on exercise performance in heart failure due to dilated cardiomyopathy or ischemic heart disease

Peripheral adaptations and ventricular abnormalities influence physical performance in chronic heart failure. However, the role of the heart in determining exercise capacity has not been completely elucidated. To define cardiac determinants of exercise capacity in patients with dilated cardiomyopathy. In 101 patients with heart failure (NYHA class II-III) due to primary or ischemic dilated cardiomyopathy we measured peak exercise oxygen consumption (Pvo2), left ventricular ejection fraction (EF), left and right atrial and ventricular cavity dimensions, mitral and tricuspid flows. Patients were subdivided in class A (Pvo2 > 20 ml/min per kg; n = 44), class B (Pvo2 16-20 ml/min per kg; n = 42) and class C (Pvo2 < 16 ml/min per kg; n = 15). Left ventricular diastolic and systolic dimensions, left atrial diameter, right atrial and ventricular areas were greater in class C than in class B and A; EF was lower in class C than in the other two classes; mitral peak flow velocity at early diastole (PFVE) and the ratio between early and late peak flow velocity (PFVE/PFVA) were higher in class C; mitral and tricuspid deceleration time (DT) in class B and A significantly exceeded those in class C. Peak vo2 was correlated with left and right ventricular dimensions, left atrial diameter, EF, mitral PFVE and PFVE/PFVA, mitral and tricuspid DT. Left ventricular EF, DT of the mitral valve and left ventricular diastolic diameter were independent predictors of peak vo2 at multivariate analysis. In patients with dilated cardiomyopathy Pvo2 is related to left and right ventricular dimensions, left and right ventricular filling pattern and EF. Both systolic and diastolic dysfunction influence functional capacity.

Peripheral vascular resistance limits exercise functional capacity of mild hypertensives.

To evaluate the physiological basis for suboptimal peak exercise oxygen consumption (VO2p) observed in the early stage of hypertension, 25 WHO Stage I hypertensive men with normal left ventricular mass and 10 healthy control subjects of equivalent age underwent the maximal cardiopulmonary exercise test with contemporary measurement of cardiac output with Tc99m angiocardiography. At peak exercise hypertensive patients had lower VO2p (p < 0.045) and cardiac output (p < 0.014) and higher vascular resistance (p < 0.010) than controls. At multiple regression analysis VO2 was positively related to cardiac output in controls (r = 0.80, p < 0.02), whereas in hypertensives the best (negative) correlation was observed with peripheral vascular resistance (r = -0.72, p < 0.04). Thus reduced cardiopulmonary function during physical exercise in hypertensives seems to be mainly related to impaired peripheral vascular autoregulation.

Maximal Exercise Testing for the Selection of Heart Transplantation Candidates: Limitation of Peak Oxygen Consumption

Peak exercise oxygen consumption (peak VO2), which is considered an indicator of prognosis in advanced heart failure, is currently being used as a major criterion in many centers for the selection of candidates for heart transplantation. Available studies suggest that patients with peak VO2 < 14 mL/min/kg have improved survival and significant functional benefit with transplantation. Since patients may terminate symptom-limited exercise tests for a variety of reasons, peak VO2 does not necessarily reflect maximal VO2, leading to the possibility of inappropriate selection for transplantation. Therefore, we investigated the proportion of transplant candidates referred for exercise testing considered to have achieved maximal results from studies. Fifty-five patients with heart failure, aged 51+/-9 years, (mean +/- SD) underwent maximum symptom-limited exercise tests on a cycle ergometer utilizing a Jones stage 1 incremental protocol. Tests were considered maximal if subjects achieved peak heart rate (HR) > 85% predicted ("cardiocirculatory limitation") or peak minute ventilation (VE) > 85% predicted ("ventilatory limitation"), and achieved an anaerobic threshold (AT) by noninvasive measures. Seven tests were terminated because of chest pain, ST-segment abnormalities, or ventricular arrhythmias. Of the remaining 48 studies, the reasons for stopping exercise were leg fatigue in 52%, dyspnea in 16%, and both symptoms in 23%. Sixteen of the 48 patients (33%) had peak VO2 < 14 mL/min/kg. In 8 of these 16 patients, both peak HR and VE were < 85% predicted. Of these eight without apparent HR or ventilatory limitation, none had oxygen desaturation below 90% or fall in BP, two were in atrial fibrillation, and only three had evidence that an AT was achieved. Among the patients with peak VO2 < 14 mL/min/kg, there were no objective signs of a cardiocirculatory or a respiratory limitation to exercise in half of them, and 31% did not achieve an AT either, thus not meeting any criteria to support evidence of maximal exercise. Exercise tests without objective evidence of cardiocirculatory or ventilatory limitation may not represent maximal performance. Consequently, peak VO2 may misclassify an appreciable proportion of candidates if the test results are submaximal. Clinical exercise studies indicating low peak VO2 must be interpreted in the context of whether a defined objective exercise limitation is evident to avoid biasing the selection of heart transplant candidates.

Predictors of primary atrial fibrillation and concomitant clinical and hemodynamic changes in patients with chronic heart failure: a prospective study in 344 patients with baseline sinus rhythm

Objectives. This study investigated the incidence, predisposing factors and significance of the onset of atrial fibrillation (AF) in patients with chronic congestive heart failure (CHF).Background. The association between CHF and AF is well documented, but the factors that predispose to the onset of the arrhythmia and its impact remain controversial.Methods. We prospectively followed up 344 patients with CHF and sinus rhythm (SR). Over a period of 19 ± 12 months (mean ± SD), 28 patients developed atrial fibrillation (AF), which became chronic in 18.Results. At baseline, no differences were found in any clinical and hemodynamic variables between patients who developed chronic AF and those who did not. Reversible AF occurring during follow-up and lower mitral flow velocity at atrial contraction as detected at the last evaluation in SR were independent predictors of the subsequent development of chronic AF. When AF occurred, New York Heart Association functional class worsened (from 2.4 ± 0.5 to 2.9 ± 0.6, p = 0.0001), peak exercise oxygen consumption declined (from 16 ± 5 to 11 ± 5 ml/kg per min, p = 0.002), cardiac index decreased (from 2.2 ± 0.4 to 1.8 ± 0.4, p = 0.0008), and mitral and tricuspid regurgitation increased (from grade 1.8 ± 1.1 to grade 2.4 ± 1.4, p = 0.0001 and from grade 1.0 ± 1.2 to grade 1.8 ± 1.2, p = 0.001, respectively). Systemic thromboembolism occurred in 3 of the 18 patients with AF. Nine of 18 patients died after AF, and the occurrence of AF was a predictor of major cardiac events.Conclusions. In patients with CHF, reversible AF and reduction of left atrial contribution to left ventricular filling predict the subsequent development of chronic AF. The onset of AF is associated with clinical and hemodynamic deterioration and may predispose to systemic thromboembolism and poorer prognosis.

Cardiopulmonary exercise testing identifies low risk patients with heart failure and severely impaired exercise capacity considered for heart transplantation.

The 3-year survival rates of 500 patients with congestive heart failure (CHF) referred for heart transplantation were assessed to evaluate the clinical and exercise variables most useful for estimating prognostic risk. Detailed prognostic risk stratification of patients with a peak exercise oxygen consumption (VO2) < or = 14 ml/min per kg to identify lower risk patient subsets has been limited in earlier series by relatively small sample size. Cardiopulmonary exercise testing was performed in 500 patients with CHF referred for heart transplantation; 154 (31%) had a peak exercise VO2 < or = 14 ml/min per kg. Univariate and multivariate analyses were performed to identify the 3-year prognostic risk. The 55% 3-year survival rate of the 77 patients with a peak exercise VO2 < or = 14 ml/min per kg unable to reach a peak exercise systolic blood pressure (SBP) of 120 mm Hg was significantly lower than the 83% survival rate in the 74 patients able to reach this exercise blood pressure (p = 0.004). Multivariate analysis revealed that peak exercise SBP (p = 0.0005) and percent predicted peak VO2 < or = 50% (p = 0.04) were the two most important predictors for the combined end point of death or listing as Status 1. Peak exercise SBP and percent predicted peak exercise VO2 are two inexpensive and easily measured noninvasive variables that can be used to further prognostically risk stratify ambulatory patients with CHF referred for heart transplantation with a peak exercise VO2 < or = 14 ml/min per kg.

Peak Exercise Oxygen Consumption in Chronic Heart Failure: Toward Efficient Use in the Individual Patient

Objectives. This study sought to 1) assess the short-, medium- and long-term prognostic power of peak oxygen consumption (V̇o2) in patients with heart failure; 2) verify the consistency of a nonmeasurable anaerobic threshold (AT) as a criterion of nonapplicability of peak V̇o2; 3) develop simple rules for the efficient use of peak V̇o2in individualized prognostic stratification and clinical decision making.Background. Peak V̇o2, when AT is identified, is among the indicators for heart transplant eligibility. However, in clinical practice the application of defined peak V̇o2cutoff values to all patients could be inappropriate and misleading.Methods. Six hundred fifty-three patients consecutively considered for eligibility for heart transplantation were followed up. Outcomes (cardiac death and urgent transplantation) were determined when all survivors had a minimum of 6 months of follow-up.Results. Contraindication to the exercise test identified very high risk patients. The relatively small sample of women did not allow inferences to be drawn. In men, peak V̇o2stratified into three levels (≤10, 10 to 18 and >18 ml/kg per min) identified groups at high, medium and low risk, respectively. The prognostic power of peak V̇o2≤10 ml/kg per min was maintained even when the AT was not detected. In patients in New York Heart Association functional class III or IV, peak V̇o2did not have prognostic power. In patients in functional class I or II, peak V̇o2stratification was prognostically valuable, but less so at 6 than at 12 or 24 months. Age did not influence peak V̇o2prognostic stratification.Conclusions. A contraindication to exercise testing should be considered a priority for listing patients for heart transplantation. Only in less symptomatic male patients does a peak V̇o2≤10 ml/kg per min identify short-, medium- and long-term high risk groups. A peak V̇o2>18 ml/kg per min implies good prognosis with medical therapy.