Physical activity is associated with positive responses during carotid sinus massage and head-up tilt-table test in patients with unexplained syncope.

AIMS: Physical exercise is known to alter the physiological response to orthostatic stress. This study compared reported physical activity levels in patients with unexplained syncope who did or did not demonstrate positive responses to carotid sinus massage and head-up tilt-table testing. METHODS: We reviewed the records of 1,336 patients with unexplained syncope who underwent carotid sinus massage and head-up tilt-table testing. Patients with positive responses (cases) were compared with patients with negative responses (controls). Multivariable regression analysis was used to identify independent predictors of positive responses to carotid sinus massage and head-up tilt-table testing. RESULTS: Seventy patients had a positive response to carotid sinus massage and 564 patients had a positive response to head-up tilt-table testing. Physical activity was an independent positive predictor of a positive response to both carotid sinus massage {adjusted odds ratio (AOR) 1.86, 95% CI (1.14-3.05); p = 0.01} and head-up tilt-table testing {AOR 1.31, 95% CI (1.04-1.65); P = 0.02} even after adjustment for multiple other factors including age, gender, and other medical conditions. CONCLUSION: Physical activity is associated with greater likelihood of positive responses during carotid sinus massage and head-up tilt-table testing.

Telomere length and cardiorespiratory fitness in marathon runners.

BACKGROUND AND AIM: Physical exercise up-regulates telomere-stabilizing proteins in mice, suggesting that physical activity affects telomere length. Several human studies assessing the relationship between physical activity, measured by health or activity surveys, and telomere length have produced conflicting results. The present study sought to explore the association between telomere length and physical fitness measured objectively as maximal oxygen uptake in endurance-trained athletes and sedentary controls. METHODS: Seventeen marathon runners and 15 age- and sex-matched healthy, sedentary control subjects participated in the study. Medical history, demographic information, maximal oxygen uptake (VO2 max), and peripheral blood lymphocyte telomere length were measured in all subjects. Statistical analysis was performed to examine the relationship between telomere length and measured variables. RESULTS: Athletes and sedentary controls had similar lymphocyte (0.97 ± 0.20 vs 1.01 ± 0.18; P = 0.6) and granulocyte (0.89 ± 0.11 vs 0.89 ± 0.12; P = 0.9) telomere lengths. Linear regression analysis showed age as the only variable significantly associated with telomere length (P = 0.007). There was no correlation between VO2 max and telomere length. CONCLUSION: In a cohort of healthy adult athletes and sedentary controls, there was no association between physical activity measured by VO2 max and peripheral blood lymphocyte and granulocyte telomere length.

Clinical value of stress-only Tc-99m SPECT imaging: importance of attenuation correction.

BACKGROUND: In selected patients, stress-only SPECT imaging has been proposed as an alternative to rest-stress SPECT imaging to improve laboratory efficiency and reduce radiation exposure. The impact of attenuation correction (AC) upon interpretation, post-test patient management and cardiac risk stratification in relation to stress-only imaging is not well understood. OBJECTIVES: The purpose of this study was to determine the clinical value for laboratory throughput and predicting outcomes of normal and abnormal stress-only SPECT imaging with AC in a consecutive series of clinically referred patients. METHODS: A retrospective analysis of 1,383 consecutive patients who were scheduled for stress-only SPECT imaging for symptom assessment of suspected myocardial ischemia was performed. All images had been interpreted and categorized using the standard 17-segment model without AC followed by AC. Follow-up data for 2.1 ± 1.3 years after SPECT imaging for the occurrence of cardiac events (non-fatal MI, cardiac death, and cardiac revascularization) previously collected by routine methods were reviewed. RESULTS: Non-AC SPECT image interpretation revealed that 58% (802/1383) of patients had abnormal stress images. AC image interpretation of the abnormal non-AC images re-classified 83% (666/802) of these as normal. Among patients with abnormal stress images after AC (136/1383), 63% (86/136) returned for additional rest scans, while the remaining 37% (50/136) were clinically managed without further rest images. The incidence of cardiac death or non-fatal MI was very low in patients with normal stress-only scans (0.7%). CONCLUSION: A strategy of stress-only imaging with AC in symptomatic patients is an efficient method which appropriately identifies at risk and low-risk patients yielding a low percentage requiring rest imaging. Clinical decisions can be made based on abnormal stress-only imaging without further rest imaging if clinically appropriate.

A strategy of symptom-limited exercise with regadenoson-as-needed for stress myocardial perfusion imaging: a randomized controlled trial.

BACKGROUND: Ambulatory patients with uncertain functional capacity may benefit from combined exercise and vasodilator stress protocols for myocardial perfusion imaging (MPI). The safety and MPI image quality with regadenoson administered during symptom-limited exercise have not been prospectively evaluated. METHODS AND RESULTS: A total of 140 patients (mean age 61 years, 48% female) referred for exercise with vasodilator stress MPI were randomized 2:1 to a strategy of exercise with regadenoson-as-necessary (Ex-Reg, n = 96) or dipyridamole with exercise (Dip-Ex, n = 44) after Duke Activity Status Index (DASI) scoring (median score 28 vs 24, P = .09). Ex-Reg subjects commenced treadmill exercise and regadenoson was administered only if the subject was unable to reach standard endpoints. Dip-Ex subjects received dipyridamole prior to symptom-limited exercise. Hemodynamics were recorded throughout. Subjects completed symptom questionnaires and MPI image quality was assessed by blinded read. Ex-Reg subjects were more likely to achieve ≥85% age-predicted maximum heart rate than Dip-Ex subjects (57% vs 32%, P < .01). Only 50% of subjects meeting inclusion criteria and randomized to Ex-Reg required regadenoson and none had symptomatic hemodynamic changes. Severe side effects or adverse events occurred in 16% of Ex-Reg and 24% of Dip-Ex subjects (P = .12). MPI image quality was "good" or "excellent" in 88% of Ex-Reg subjects and 86% of Dip-Ex subjects (P = .33). CONCLUSION: A strategy of exercise with regadenoson-as-needed for MPI offers similar safety and side effect profile with similar image quality compared to dipyridamole with exercise, with reduced pharmaceutical use.

The clinical value of single photon emission computed tomography myocardial perfusion imaging in cardiac risk stratification of very elderly patients (≥80 years) with suspected coronary artery disease.

BACKGROUND: The role of single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) in cardiac evaluation of the very elderly patients is unclear. We investigated the clinical value of SPECT MPI in very elderly patients (≥80 years) with suspected coronary artery disease (CAD) as well as in comparison to younger patients. METHODS AND RESULTS: A retrospective analysis of prospectively collected data from 8,864 patients [1,093 patients ≥80 years (very elderly), 3,369 patients 65-79 years (elderly), and 4,402 patients 50-64 years (middle-aged)] with suspected CAD who underwent exercise and/or pharmacologic stress testing with SPECT MPI between 1996 and 2005 was performed. Clinical and SPECT MPI characteristics, cardiac event rates, early (≤60 days) cardiac catheterization and revascularization rates of very elderly patients were compared to that of younger patients. Mean follow-up for cardiac events (cardiac death or non-fatal myocardial infarction) was 1.9 ± 0.9 years. Very elderly patients with moderate to severely abnormal SSS had a significantly higher annualized cardiac event rate than those with mildly abnormal or normal study (9.6% vs 3.4% and 2.5% respectively, P < .001). Across all categories of SSS, very elderly patients had a significantly higher cardiac event rate as compared to younger patients (P < .001). Early cardiac catheterization and revascularization referrals in very elderly patients increased as a function of severity of ischemia on SPECT MPI (P < .001), although these referral rates were significantly lower in very elderly patients with mild to moderate and severe ischemia as compared to younger patients (P < .05). CONCLUSIONS: In very elderly patients (≥80 years) with suspected CAD, SPECT MPI has prognostic and incremental value in the noninvasive cardiovascular assessment for risk stratification and may influence medical decisions.

Relation of vitamin D level to maximal oxygen uptake in adults.

Low cardiorespiratory fitness and low serum 25-hydroxy vitamin D (25[OH]D) levels are associated with increased cardiovascular and all-cause mortality, but whether low 25(OH)D is independently associated with cardiorespiratory fitness in healthy adults is not known. We examined 25(OH)D levels and fitness in 200 healthy adults participating in a double-blind clinical trial investigating statins and muscle performance (STOMP study). Maximal aerobic exercise capacity (Vo2(max)) was measured using metabolic gas analysis during graded treadmill exercise to exhaustion. 25(OH)D was measured using an enzyme-linked immunosorbent assay. Daily physical activity was assessed using the Paffenbarger Physical Activity Questionnaire. Serum 25(OH)D concentration was positively related to Vo2(max) (r = 0.29, p = 0.0001), even after adjusting for relevant predictors (e.g., age, gender, and body mass index). There was also a significant interaction between 25(OH)D level and self-reported hours of moderate to vigorous physical activity (MVPA; p < 0.02). With each SD increase in 25(OH)D, Vo2(max) increased by 2.6 ml/kg/min (p = 0.0001) when MVPA was low (16 hours/week) and 1.6 ml/kg/min (p <0.0004) when MVPA was moderate (35 hours/week) but only 0.01 ml/kg/min (p = 0.9) when MVPA was high (64 hours/week). In conclusion, serum 25(OH)D levels predict Vo2(max) in adults; the effect is greatest in those with low levels of physical activity.

Blunted heart rate response as a predictor of cardiac death in patients undergoing vasodilator stress technetium-99m sestamibi gated SPECT myocardial perfusion imaging.

INTRODUCTION: The prognostic value of a blunted heart rate response (BHR) during ECG-gated vasodilator stress SPECT MPI in relation to ventricular function on long-term cardiovascular events is not well established. We performed this study to evaluate the incremental prognostic value of BHR during pharmacological stress SPECT MPI. METHODS: Consecutive patients who underwent dipyridamole stress Tc-99m sestamibi ECG-gated SPECT MPI (without exercise) were identified. The ratio of peak stress heart rate to baseline was noted. If the ratio was <1.20, it was considered blunted (BHR). The images were interpreted using the standard ASNC 17 segment model. Patients were followed up for a mean time period of 2.3 +/- 1.5 years. RESULTS: Sixty-four percent (2,890/4,484) of patients demonstrated BHR during dipyridamole stress testing. Cardiac death, the primary end point, occurred in 6.8% of patients. Patients with BHR had a significantly lower cardiac death-free survival as compared to NO BHR group in total population (83% vs 94%; P < .001) as well as in subgroup with normal ejection fraction (89% vs 96%; P < .001). BHR was an independent predictor of cardiac death after adjusting for multiple clinical, perfusion, and function-related gated SPECT variables. CONCLUSION: Blunted heart rate response during vasodilator stress SPECT MPI is an important prognostic marker for cardiac death.