Sherry Pinkstaff

Determining the Preferred Percent-Predicted Equation for Peak Oxygen Consumption in Patients With Heart Failure

Background—Peak oxygen consumption (Vo2) is routinely assessed in patients with heart failure undergoing cardiopulmonary exercise testing. The purpose of the present investigation was to determine the prognostic ability of several established peak Vo2 prediction equations in a large heart failure cohort. Methods and Results—One thousand one hundred sixty-five subjects (70% males; age, 57.0±13.8 years; ischemic etiology, 43%) diagnosed with heart failure underwent cardiopulmonary exercise testing. Percent-predicted peak Vo2 was calculated according to normative values proposed by Wasserman and Hansen (equation), Jones et al (equation), the Cooper Clinic (below low fitness threshold), a Veteran’s Administration male referral data set (4 equations), and the St James Take Heart Project for women (equation). The prognostic significance of percent-predicted Vo2 values derived from the 2 latter, sex-specific equations were assessed collectively. There were 179 major cardiac events (117 deaths, 44 heart transplantations, and 18 left ventricular assist device implantations) during the 2-year tracking period (annual event rate, 10%). Measured peak Vo2 and all percent-predicted peak Vo2 calculations were significant univariate predictors of adverse events (&khgr;2≥31.9, P<0.001) and added prognostic value to ventilatory efficiency (VE/Vco2 slope), the strongest cardiopulmonary exercise testing predictor of adverse events (&khgr;2=150.7, P<0.001), in a multivariate regression. The Wasserman/Hansen prediction equation provided optimal prognostic information. Conclusions—Actual peak Vo2 and the percent-predicted models included in this analysis all were significant predictors of adverse events. It seems that the percent-predicted peak Vo2 value derived from the Wasserman/Hansen equations may outperform other expressions of this cardiopulmonary exercise testing variable.

The partial pressure of resting end-tidal carbon dioxide predicts major cardiac events in patients with systolic heart failure

BACKGROUND The resting partial pressure of end-tidal carbon dioxide (Petco2) has been shown to reflect cardiac performance in acute care settings in patients with heart failure (HF). The purpose of the present study was to compare the prognostic ability of the partial pressure of Petco2 at rest to other commonly collected resting variables in patients with systolic HF. METHODS A total of 353 patients (mean age 58.6+/-13.7, 72% male) with systolic HF were included in this study. All patients underwent cardiopulmonary exercise testing where New York Heart Association (NYHA) class, resting Petco2, peak oxygen consumption, and the minute ventilation/carbon dioxide production slope were determined. Subjects were then followed for major cardiac events (mortality, left ventricular assist device implantation implantation, urgent heart transplantation). RESULTS There were 104 major cardiac events during the 23.6+/-17.0-month tracking period. Multivariate Cox regression analysis revealed NYHA class (chi2 28.7, P<.001), left ventricular ejection fraction (residual chi2 21.7, P<.001), and resting Petco2 (residual chi2 14.1, P<.001) were all prognostically significant and retained in the regression. In a separate Cox regression analysis, left ventricular ejection fraction (residual chi2 8.8, P=.003), NYHA class (residual chi2 7.7, P=.005), and resting Petco2 (residual chi2 5.7, P=.02) added prognostic value to the minute ventilation/carbon dioxide production slope (chi2 26.0, P<.001). CONCLUSION Resting Petco2 can be noninvasively collected from subjects in a short period, at a low cost, and with no risk or discomfort to the patient. Given the prognostic value demonstrated in the present study, the clinical assessment of resting Petco2 in the HF population may be warranted.

Influence of Etiology of Heart Failure on the Obesity Paradox

Several investigations have demonstrated that higher body weight, as assessed by the body mass index, is associated with improved prognosis in patients with heart failure (HF). The purpose of the present investigation was to assess the influence of HF etiology on the prognostic ability of the body mass index in a cohort undergoing cardiopulmonary exercise testing. A total of 1,160 subjects were included in the analysis. All subjects underwent cardiopulmonary exercise testing, at which the minute ventilation/carbon dioxide production slope and peak oxygen consumption were determined. In the overall group, 193 cardiac deaths occurred during a mean follow-up of 30.7 +/- 25.6 months (annual event rate 6.0%). The subjects classified as obese consistently had improved survival compared to those classified as normal weight (overall survival rate 88.0% vs <or=81.1%, p <0.001). Differences in survival according to HF etiology were observed for those classified as overweight. In the ischemic subgroup, the survival characteristics for the overweight subjects (75.5%) were similar those for subjects classified as normal weight (81.1%). The converse was true for the nonischemic subgroup, for whom the survival trends for the obese (86.4%) and overweight subjects (88.4%) were similar. The minute ventilation/carbon dioxide production slope was the strongest prognostic marker (chi-square >or=43.4, p <0.001) for both etiologies, and the body mass index added prognostic value (residual chi-square >or=4.7, p <0.05). In conclusion, these results further support the notion that obesity confers improved prognosis in patients with HF, irrespective of the HF etiology. Moreover, the body mass index appears to add predictive value during the cardiopulmonary exercise testing assessment. However, survival appears to differ according to HF etiology in subjects classified as overweight.

Quantifying Exertion Level During Exercise Stress Testing Using Percentage of Age-Predicted Maximal Heart Rate, Rate Pressure Product, and Perceived Exertion

OBJECTIVE To determine if the attainment of at least 85% of age-predicted maximal heart rate (APMHR), using the equation 220 - age, and/or at least 25,000 as the product of maximal heart rate and systolic blood pressure (rate pressure product, RPP) is an accurate indicator of exertion level during exercise stress testing. PATIENTS AND METHODS From May 1, 2009, to February 15, 2010, 238 patients (mean ± SD age, 49.3±11.9 years; 50% male) with symptoms suggestive of myocardial ischemia underwent an exercise stress test with the addition of ventilatory expired gas analysis and a myocardial perfusion study. Ventilatory expired gas analysis determined the peak respiratory exchange ratio (RER), which is considered a valid and reliable variable for quantifying a patients exertion during exercise. RESULTS Of the patients, 207 (87%) attained a peak RER of 1.00 or more, and 123 (52%) attained a peak RER of 1.10 or more. An APMHR of 85% or more and peak RPP of 25,000 or more were both ineffective in identifying patients who put forth a maximal exercise effort (ie, peak RER, ≥1.10). Perceived exertion was a significant indicator (P=.04) of patient exertion, with a threshold of 15 (6-20 scale) being an optimal cut point. The percentage of equivocal myocardial perfusion study results was significantly higher in patients who demonstrated a submaximal exercise effort by peak RER (P≤.007). CONCLUSION Aerobic exercise testing is an integral component in the assessment of patients with suspected myocardial ischemia. Our findings indicate that the currently used percentage of APMHR and peak RPP thresholds are ineffective in quantifying a patients level of exertion during exercise stress testing.

Prognostic value of timing and duration characteristics of exercise oscillatory ventilation in patients with heart failure.

BACKGROUND Exercise oscillatory ventilation (EOV) occurs in a sub-group of patients with increased heart failure (HF) severity and poorer prognosis. The purpose of this investigation was to examine the prognostic value of the largest ventilatory oscillation characteristics in HF patients. METHODS One hundred fifty-four subjects diagnosed with HF underwent cardiopulmonary exercise testing. Subjects with EOV were then divided into two sub-groups: (1) largest ventilatory oscillation during the first half of exercise with an oscillation width > or =30 seconds; and (2) largest ventilatory oscillation during the second half of exercise or an oscillation width <30 seconds. Subjects were tracked for major cardiac events after the exercise test. RESULTS The fifty-five subjects (35.7%) in the overall group demonstrating EOV during the exercise test were at significantly higher risk for adverse events (hazard ratio = 3.0, 95% confidence interval 1.6 to 5.5, p < 0.001). The prognostic value of this ventilatory phenomenon improved when only subjects with the largest ventilatory oscillation during the first half of exercise with an oscillation width > or =30 seconds were defined as having EOV (hazard ratio = 3.6, 95% confidence interval 1.6 to 7.9, p = 0.002). CONCLUSIONS In this study we found that the characteristics of the largest oscillatory ventilation provide valuable prognostic information in patients with EOV.

Defining the Optimal Prognostic Window for Cardiopulmonary Exercise Testing in Patients with Heart Failure

Background—Ventilatory efficiency (Ve/Vco2 slope) and peak oxygen consumption (Vo) provide robust prognostic information in patients with heart failure undergoing cardiopulmonary exercise testing (CPX). The purpose of this study is to assess the change in prognostic characteristics of CPX at different time intervals. Methods and Results—Seven hundred ninety-one subjects (74% male, mean age: 60.7±12.9 years, ejection fraction: 34.6±15.0%, ischemic etiology: 51%) underwent CPX and were tracked for major cardiac events over a 4-year period. All event-free subjects were tracked for at least 3 years. Mean Ve/Vco2 slope and peak Vo2 were 35.0±10.0 and 16.0±6.4 mL O2 · kg−1 · min−1, respectively. There were a total of 263 major cardiac events (199 deaths, 45 transplants, and 19 left ventricular assist device implantations). Both continuous and dichotomous expressions of the Ve/Vco2 slope and peak Vo2 were prognostically significant up to 18 months post-CPX. Continuous and dichotomous expressions of the Ve/Vco2 slope remained prognostically significant up to 36 months post-CPX, whereas peak Vo2 was not predictive during the third and fourth year of follow-up. In a multivariate analysis, the Ve/Vco2 slope was consistently the superior prognostic marker, whereas peak Vo2 added predictive value and was retained in the regression up to 18 months post-CPX. Conclusions—These results indicate that commonly assessed CPX variables retain prognostic value for at least 2 years. The Ve/Vco2 slope is the superior predictor of adverse events throughout follow-up, although peak Vo2 provides additive prognostic information during the first 2 years of follow-up.

Current trends in reducing cardiovascular risk factors in the United States: focus on worksite health and wellness.

Health care in the United States (US) is changing with a broad provision of health care services to every American due to the Affordable Care Act (ACA) slated to begin in January of 2014. An important aspect of the ACA is that US companies may begin to offer health insurance incentives to employees for participating in health and wellness initiatives. Moreover, since US employers directly absorb many of the financial costs associated with the high degree of cardiovascular (CV) risk factors present in their personnel, employers may be financially vested in improving employee health. However, employers must also consider the costs of developing and maintaining programs to improve employee health and their return on investment (ROI). This review will identify key risk factors to address in a worksite health and wellness program and to examine the performance of such programs in improving CV risk factors and their ROI.

Usefulness of decrease in oxygen uptake efficiency slope to identify myocardial perfusion defects in men undergoing myocardial ischemic evaluation.

Cardiopulmonary exercise testing (CPX) might aid in the diagnosis of coronary artery disease. However, a heterogeneous clinical population without previous workup bias has not been studied nor has a more extensive list of CPX variables. A total of 303 subjects (age 49.9 ± 11.6 years, 157 men) with symptoms suggestive of coronary artery disease underwent CPX and a single photon emission computed tomographic myocardial perfusion study (MPS). Ventilatory efficiency was calculated using the oxygen uptake efficiency slope (OUES). The change in the OUES was calculated by subtracting the OUES response during the first 50% of CPX from the OUES obtained during the last 25% of CPX. A negative change in the OUES (< 0) from the first 50% to the last 25% of CPX was predictive of positive MPS findings only in the male subjects. The diagnostic significance of the change in OUES in men was found for any level (including equivocal studies) of positive MPS findings (area under the curve 0.67, 95% confidence interval 0.59 to 0.76, p < 0.0001) and was even stronger in those with a more definitive (excluding equivocal studies) perfusion defect (area under the curve 0.76, 95% confidence interval 0.67 to 0.85; relative risk 5.4, 95% confidence interval 2.1 to 13.8, p < 0.0001). In conclusion, this is the first time that a change in ventilatory efficiency, assessed using the OUES, has been shown to be predictive of positive MPS findings However, the OUES change only provided diagnostic information for men, a finding that warrants additional analysis.

Six months of Sildenafil therapy improves heart rate recovery in patients with heart failure

Previous research has demonstrated an increase in large vessel stiffness in patients with heart failure (HF). Furthermore, heart rate recovery (HRR) may be negatively impacted by increased arterial stiffness secondary to altered baroreceptor discharge. The purpose of the present study was to determine if chronic phosphodiesterase 5 (PDE5) inhibition with Sildenafil, previously shown to improve arterial stiffness, favorably impacts HRR in patients with HF. Forty male subjects (age: 65.3+/-7.3 years, baseline ejection fraction: 37.1+/-7.4%, 15 non-ischemic HF/25 ischemic HF) participated in this study. Subjects received Sildenafil (25 mg, 3 times/day) for six months. Symptom-limited exercise testing was performed at baseline and six months with a lower extremity ergometer. Heart rate recovery was defined as HR at maximal exercise minus HR at 1 min recovery. No adverse effects were reported throughout the study period. Paired t-testing revealed that HRR was significantly improved following six months of Sildenafil therapy (baseline: 17.5+/-3.5 bpm vs. Post: 20.6+/-3.2 bpm). The results of the present study indicate that chronic Sildenafil therapy significantly increases HRR, an important prognostic marker, in patients with HF. A plausible mechanism for the improvement of HRR is the previously demonstrated impact Sildenafil has on arterial stiffness and therefore baroreceptor function.

Neuromuscular electrical stimulation and inspiratory muscle training as potential adjunctive rehabilitation options for patients with heart failure.

Aerobic and resistance exercise training programs produce an abundance of physiologic and clinical benefits in patients with heart failure (HF). Improved maximal aerobic capacity, submaximal aerobic endurance, muscle force production, perceived quality of life, and skeletal muscle characteristics are among the more established outcomes resulting from these rehabilitation techniques. Moreover, both aerobic and resistance exercise training appear to portend a low risk to patients with HF when appropriate exercise prescription methods are followed. While the aforementioned training techniques will undoubtedly continue to be at the center of a well-formulated rehabilitation program, other adjunctive interventions, which are presently underutilized in clinical practice, may prove beneficial in patients with HF. Specifically, both neuromuscular electrical stimulation (NMES) and inspiratory muscle training (IMT) appear to significantly improve several physiologic, exercise, symptomatologic, and quality-of-life parameters. NMES targets skeletal muscle abnormalities, whereas IMT primarily targets the weakened respiratory musculature, both often encountered in patients with HF. A PubMed search using relevant key words identified 19 original investigations examining the impact of NMES (13 studies) and IMT (6 studies) training programs in patients with HF. The resultant review (1) provides a summary of the original research outcomes of both NMES and IMT in patients with HF; (2) addresses current research gaps, providing a direction for future investigations; and (3) provides clinical scenarios where NMES and IMT may prove to be beneficial during the rehabilitation of patients with HF.