Manfred Wonisch

Methodological approach to the first and second lactate threshold in incremental cardiopulmonary exercise testing

Determination of an ‘anaerobic threshold’ plays an important role in the appreciation of an incremental cardiopulmonary exercise test and describes prominent changes of blood lactate accumulation with increasing workload. Two lactate thresholds are discerned during cardiopulmonary exercise testing and used for physical fitness estimation or training prescription. A multitude of different terms are, however, found in the literature describing the two thresholds. Furthermore, the term ‘anaerobic threshold’ is synonymously used for both, the ‘first’ and the ‘second’ lactate threshold, bearing a great potential of confusion. The aim of this review is therefore to order terms, present threshold concepts, and describe methods for lactate threshold determination using a three-phase model with reference to the historical and physiological background to facilitate the practical application of the term ‘anaerobic threshold’.

Influence of beta-blocker use on percentage of target heart rate exercise prescription

Background Exercise is recommended for cardiac patients irrespective of beta-blockers. Percentages of maximal heart rate (%HRmax) and heart rate reserve (%HRR) are widely used to determine training intensities. The purpose of this study was to investigate the influence of chronic cardioselective beta blockade on the %HRmax and %HRR model. Methods Ten healthy male subjects randomly received oral placebo or beta-blocker bisoprolol (5 mg/day) for 2 weeks using a double-blind, crossover design. In the second week, the subjects performed a cardiopulmonary exercise test until exhaustion to determine the aerobic (AeT) and anaerobic (AnT) threshold. Results No significant differences were found for absolute and relative values of oxygen consumption, power output and ratings of perceived exertion at AeT, AnT and maximum workload. Mean HR was significantly (P < 0.05) lower at rest (−15 ± 5 bpm), AeT (−19 ± 8 bpm), AnT (− 22 ± 10 bpm) and maximal workload (−19 ± 11 bpm) with bisoprolol compared to placebo. Percentage of maximal heart rate (%HRmax) was significantly (P < 0.05) reduced at rest (43 versus 39%), AeT (64 versus 60%) and AnT (86 versus 82%), a trend for a reduction was found for %HRR at AnT (75 versus 71%, P=0.07). Conclusions Exercise prescription using %HRmax or %HRR methods are of limited accuracy for patients taking beta-blockers. Although %HRmax and %HRR are easy to determine and therefore attractive, we suggest that the most precise exercise prescription would depend on AeT and AnT. Percentages of maximal oxygen consumption or maximal workload or ratings of perceived exertion may be suggested as a substitute. Alternatively, upper limits for %HRmax and %HRR should be lower for patients taking beta-blockers.

Validation of a field test for the non-invasive determination of badminton specific aerobic performance

Aim: To develop a badminton specific test to determine on court aerobic and anaerobic performance. Method: The test was evaluated by using a lactate steady state test. Seventeen male competitive badminton players (mean (SD) age 26 (8) years, weight 74 (10) kg, height 179 (7) cm) performed an incremental field test on the badminton court to assess the heart rate turn point (HRTP) and the individual physical working capacity (PWCi) at 90% of measured maximal heart rate (HRmax). All subjects performed a 20 minute steady state test at a workload just below the PWCi. Results: Significant correlations (p<0.05) for Pearson’s product moment coefficient were found between the two methods for HR (r = 0.78) and velocity (r = 0.93). The HR at the PWCi (176 (5.5) beats/min) was significantly lower than the HRTP (179 (5.5) beats/min), but no significant difference was found for velocity (1.44 (0.3) m/s, 1.38 (0.4) m/s). The constant exercise test showed steady state conditions for both HR (175 (9) beats/min) and blood lactate concentration (3.1 (1.2) mmol/l). Conclusion: The data indicate that a valid determination of specific aerobic and anaerobic exercise performance for the sport of badminton is possible without HRTP determination.

Oral magnesium therapy, exercise heart rate, exercise tolerance, and myocardial function in coronary artery disease patients

Background: Previous studies have demonstrated that in patients with coronary artery disease (CAD) upward deflection of the heart rate (HR) performance curve can be observed and that this upward deflection and the degree of the deflection are correlated with a diminished stress dependent left ventricular function. Magnesium supplementation improves endothelial function, exercise tolerance, and exercise induced chest pain in patients with CAD. Purpose: We studied the effects of oral magnesium therapy on exercise dependent HR as related to exercise tolerance and resting myocardial function in patients with CAD. Methods: In a double blind controlled trial, 53 male patients with stable CAD were randomised to either oral magnesium 15 mmol twice daily (n = 28, age 61±9 years, height 171±7 cm, body weight 79±10 kg, previous myocardial infarction, n = 7) or placebo (n = 25, age 58±10 years, height 172±6 cm, body weight 79±10 kg, previous myocardial infarction, n = 6) for 6 months. Maximal oxygen uptake (VO2max), the degree and direction of the deflection of the HR performance curve described as factor k<0 (upward deflection), and the left ventricular ejection fraction (LVEF) were the outcomes measured. Results: Magnesium therapy for 6 months significantly increased intracellular magnesium levels (32.7±2.5 v 35.6±2.1 mEq/l, p<0.001) compared to placebo (33.1±3.1.9 v 33.8±2.0 mEq/l, NS), VO2max (28.3±6.2 v 30.6±7.1 ml/kg/min, p<0.001; 29.3±5.4 v 29.6±5.2 ml/kg/min, NS), factor k (−0.298±0.242 v −0.208±0.260, p<0.05; −0.269±0.336 v −0.272±0.335, NS), and LVEF (58±11 v 67±10%, p<0.001; 55±11 v 54±12%, NS). Conclusion: The present study supports the intake of oral magnesium and its favourable effects on exercise tolerance and left ventricular function during rest and exercise in stable CAD patients.

Effect of high-volume and -intensity endurance training in heart transplant recipients.

BACKGROUND A recommended component of heart transplant recipients (HTR) is endurance-oriented exercise therapy. However, the trainability of HTR after transplantation is vague. We examined the effect of high-volume and -intensity exercise training on exercise performance in HTR, compared with HTR undergoing regular rehabilitation training, and sedentary healthy subjects (SHS). METHODS We studied four groups of individuals; of those, three groups were HTR. Subjects were a regularly trained HTR group of denervated (HTR-D; N = 15), reinnervated (HTR-R; N = 26) hearts, a high-volume and -intensity endurance-training group (training time 7-20 h.wk(-1); HTR-ET; N = 12), and a group of sedentary healthy subjects (SHS; N = 21). All participants performed cardiopulmonary exercise testing. RESULTS The HTR-ET achieved a significantly higher performance (255 +/- 47 W, VO(2max) of 45.2 +/- 6.9 mL.kg(-1).min(-1)) in contrast to all other groups (HTR-D: 119 +/- 17 W, VO(2max) of 17.4 +/- 4.5 mL.kg(-1).min(-1); HTR-R: 119 +/- 17 W, VO(2max) of 16.9 +/- 3.7 mL.kg(-1).min(-1); SHS: 184 +/- 19 W, VO(2max) of 35.0 +/- 6.9 mL.kg(-1).min(-1)). The HR at maximal power output in the HTR-ET was 169 +/- 17 bpm and similar to SHS (164 +/- 17 bpm), but significantly higher than HTR-D (125 +/- 16) and HTR-R (142 +/- 10). Maximal lactate concentration (LAmax) of HTR-ET was 9.9 +/- 2.2 mmol.L(-1), comparable to SHS (9.2 +/- 2.1 mmol.L(-1)), and significantly higher than HTR-D (5.5 +/- 1.5 mmol.L(-1)) and HTR-R (5.1 +/- 1.0 mmol.L(-1)). CONCLUSIONS Data suggest that HTR can perform high-volume and -intensity exercise training, reaching exercise performance comparable to or even exceeding values of sedentary or moderately trained healthy subjects.

Early 4-week cardiac rehabilitation exercise training in elderly patients after heart surgery.

PURPOSE The aim of this study was to assess the effects on exercise performance of supplementing a standard cardiac rehabilitation program with additional exercise programming compared to the standard cardiac rehabilitation program alone in elderly patients after heart surgery. METHODS In this prospective, randomized controlled trial, 60 patients (32 men and 28 women, mean age 73.1 ± 4.7 years) completed cardiac rehabilitation (initiated 12.2 ± 4.9 days postsurgery). Subjects were assigned to either a control group (CG, standard cardiac rehabilitation program [n = 19]), or an intervention group (IG, additional walking [n = 19], or cycle ergometry training [n = 22]). A symptom limited cardiopulmonary exercise test and 6-minute walk test (6MWT) were performed before and after 4 weeks of cardiac rehabilitation. The MacNew questionnaire was used to assess quality of life (QOL). RESULTS At baseline, no significant differences for peak oxygen uptake (&OV0312;O2), maximal power output, or the 6MWT were detected between IG and CG. Global QOL was significantly higher in IG. After 4 weeks of cardiac rehabilitation, patients significantly improved in absolute values of the cardiopulmonary exercise test, 6MWT, and QOL scores. Significant differences between groups were found for peak &OV0312;O2 (IG: 18.2 ± 3.1 mL·kg−1·min−1 vs. CG: 16.5 ± 2.2 mL·kg−1·min−1, P < .05); maximal power output (IG: 72.2 ± 16 W vs. CG: 60.7 ± 15 W, P < .05); 6MWT (IG: 454.8 ± 76.3 m vs. CG: 400.5 ± 75.5 m, P < .05); and QOL global (IG: 6.5 ± 0.5 vs. CG: 6.3 ± 0.6, P < .05). CONCLUSION The supplementation of additional walking or cycle exercise training to standard cardiac rehabilitation programming compared to standard cardiac rehabilitation alone in elderly patients after heart surgery leads to significantly better exercise tolerance.

Clinical applications of cardiovascular magnetic resonance.

The clinical role of magnetic resonance in diseases of the heart and great vessels is rapidly evolving. Cardiovascular magnetic resonance (CMR) has become an established non-invasive imaging modality for the assessment of various cardiac disorders, such as congenital heart disease, cardiac masses, cardiomyopathies, aortic and pericardial diseases. Moreover, due to its accuracy and reproducibility, CMR is currently considered the gold standard for quantification of ventricular volumes, function, and mass. Thus, this technique is ideally suited to assess the efficacy of therapeutic interventions on ventricular hypertrophy and remodelling, which may allow a reduction in sample size to show clinically relevant effects. Comprehensive functional assessment is possible by CMR due to its capability to measure flow velocity and flow volume, which is a basic requirement to quantify lesion severity in valvular heart disease. Within the past years, major technical advances have considerably improved acquisition speed and image quality making CMR a useful tool for the evaluation of patients with ischaemic heart disease. Although the clinical robustness of coronary magnetic resonance angiography still needs improvement, CMR currently provides valuable information to detect reversible ischemia, myocardial infarction, and residual viability. In this review we will present in detail the well-established indications of CMR accompanied by an outlook on new applications that are likely to enter the clinical arena in the near future.

Cardiac rehabilitation in Austria: long term health-related quality of life outcomes

BackgroundThe goal of cardiac rehabilitation programs is not only to prolong life but also to improve physical functioning, symptoms, well-being, and health-related quality of life (HRQL). The aim of this study was to document the long-term effect of a 1-month inpatient cardiac rehabilitation intervention on HRQL in Austria.MethodsPatients (N = 487, 64.7% male, age 60.9 ± 12.5 SD years) after myocardial infarction, with or without percutaneous interventions, coronary artery bypass grafting or valve surgery underwent inpatient cardiac rehabilitation and were included in this long-term observational study (two years follow-up). HRQL was measured with both the MacNew Heart Disease Quality of Life Instrument [MacNew] and EuroQoL-5D [EQ-5D].ResultsAll MacNew scale scores improved significantly (p < 0.001) and exceeded the minimal important difference (0.5 MacNew points) by the end of rehabilitation. Although all MacNew scale scores deteriorated significantly over the two year follow-up period (p < .001), all MacNew scale scores still remained significantly higher than the pre-rehabilitation values. The mean improvement after two years in the MacNew social scale exceeded the minimal important difference while MacNew scale scores greater than the minimal important difference were reported by 40-49% of the patients.Two years after rehabilitation the mean improvement in the EQ-5D Visual Analogue Scale score was not significant with no significant change in the proportion of patients reporting problems at this time.ConclusionThese findings provide a first indication that two years following inpatient cardiac rehabilitation in Austria, the long-term improvements in HRQL are statistically significant and clinically relevant for almost 50% of the patients. Future controlled randomized trials comparing different cardiac rehabilitation programs are needed.

Comparison of effects of dalteparin and enoxaparin on hemostatic parameters and von Willebrand factor in patients with unstable angina pectoris or non--ST- segment elevation acute myocardial infarction.

The results of our study indicate that dalteparin and enoxaparin, when compared directly, have similar effects on parameters of thrombin and plasmin activation and vWF. The present study provides the first prospective, comparative results between dalteparin and enoxaparin in patients with UAP or non-ST-AMI.

Myocardial dimensions and hemodynamics during 24-h ultraendurance ergometry.

PURPOSE This study aimed to evaluate cardiorespiratory and hemodynamic responses during 24 h of continuous cycle ergometry in ultraendurance athletes. METHODS Eight males (mean ± SD; age = 39 ± 8 yr, height = 179 ± 7 cm, body weight [Wt] = 77.1 ± 6.0 kg) were monitored during 24 h at a constant workload,∼25% below the first lactate turn point at 162 ± 23 W. Measurements included Wt, HR, oxygen consumption (V˙O2), cardiac output (Q), and stroke volume (SV) determined by a noninvasive rebreathing technique (Innocor; Innovision, Odense, Denmark). Myocardial dimensions were evaluated using a two-dimensional echocardiogram. [M-mode measurement]-left atrial (LAD), ventricular end-diastolic (LVEDD), and end-systolic diameters (LVESD) were obtained over the left parasternal area. Venous blood samples were analyzed for hematocrit (Hct%), albumin (g·L(-1)), aldosterone (pg·mL(-1)), CK, CK-MB (U·L(-1)), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (pg·mL(-1)). RESULTS HR (bpm) significantly increased (P < 0.01) from 1 h (132 ± 11) to 6 h (143 ± 10) and significantly decreased (P < 0.001) from 6 to 24 h (116 ± 10). V˙O2 and (Q were unchanged during the 24 h. Wt (76.6 ± 5.6 vs 78.7 ± 5.4), SV (117 ± 13 vs 148 ± 19), LVEDD (4.9 ± 0.3 vs 5.6 ± 0.2), and LAD (3.6 ± 0.5 vs 4.3 ± 0.7) significantly increased between 6 and 24 h (P < 0.001). No significant changes were observed for LVESD. Hct (45.1 ± 1.3 vs 41.3 ± 1.2) significantly decreased (P < 0.05) and CK (181 ± 60/877 ± 515), aldosterone (48 ± 17 vs 661 ± 172), and NT-proBNP (23 ± 13 vs 583 ± 449) significantly increased (P < 0.05). The increase in SV (ΔSV) was significantly related to changes in Wt (ΔWt), and HR (ΔHR) and ΔWt were significantly related to ΔLAD and ΔLVEDD. CONCLUSION Our findings suggest that the decrease in HR during 24 h of ultraendurance exercise was due to hypervolemia and the associated ventricular loading, increasing left ventricular diastolic dimensions because of increased SV and LVEDD, resulting in an increase in NT-proBNP.