Risk stratification using line source attenuation correction with rest/stress Tc-99m sestamibi SPECT myocardial perfusion imaging.

BACKGROUND: Although line source attenuation correction (AC) in SPECT MPI studies improves diagnostic accuracy, its prognostic value is less understood. METHODS: Consecutive patients (n = 6,513) who underwent rest/stress AC ECG-gated SPECT MPI were followed for cardiac death or non-fatal myocardial infarction (MI). A 17-segment model and AC summed stress score (SSS) were used to classify images. RESULTS: Of the 6,513 patients, cardiac death or non-fatal MI occurred in 267 (4.1%), over 2.0 ± 1.4 years. The AC-SSS in patients with a cardiac event (5.6 ± 7.8) was significantly higher than in those without (1.9 ± 4.6, P < .001). The annualized cardiac event rate in patients with an AC-SSS 1-3 (3.6%) was significantly higher than in those with an AC-SSS = 0 (1.1%, P < .001) but similar to that in those with an AC-SSS 4-8 (2.9%, P = .4). Accordingly, patients were classified to AC-SSS = 0, 1-8, and >8 with annualized cardiac event rates of 1.1%, 3.2%, and 8.5%, respectively (P < .0001). In multivariate analysis, an AC-SSS 1-8 and >8 emerged as independent predictors of cardiac events (P < .02 and P < .0001, respectively). CONCLUSION: Rest/stress ECG-gated SPECT MPI with line source AC provides highly effective and incremental risk stratification for future cardiac events.

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.

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.

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.

Obesity and outcomes among patients with established atrial fibrillation.

Atrial fibrillation (AF) and obesity have reached epidemic proportions. The impact of obesity on clinical outcomes in patients with established AF is unknown. We analyzed 2,492 patients in the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) study. Body mass index (BMI) was evaluated as a categorical variable (normal 18.5 to <25 kg/m(2), overweight 25 to <30 kg/m(2), obese >or=30 kg/m(2)). Rate of death from any cause was higher in the normal BMI group (5.8 per 100 patient-years) than in the overweight and obese groups (3.9 and 3.7, respectively). Cardiovascular death rate was highest in the normal BMI group (3.1 per 100 patient-years), lowest in the overweight group (1.5 per 100 patient-years), and intermediate in the obese group (2.1 per 100 patient-years). After adjustment for baseline factors, differences in risk of death from any cause were no longer significant. However, overweight remained associated with a lower risk of cardiovascular death (hazard ratio 0.47, p = 0.002). Obese patients were more likely to have an uncontrolled heart rate at rest, but rhythm-control strategy success was similar across BMI categories. In each BMI category, risk of death from any cause was similar for patients randomized to a rhythm- or rate-control strategy. In conclusion, in patients with established AF, overweight and obesity do not adversely affect overall survival. Obesity does not appear to affect the relative benefit of a rate- or rhythm-control strategy.

Distal renal tubular acidosis in lymphoplasmacytic lymphoma Waldenström's macroglobulinemia: a case report.

We present a case of distal renal tubular acidosis and acute renal insufficiency in a patient with Waldenström's macroglobulinemia. Distal renal tubular acidosis has been described in hypergammaglobulinemia, but not in patients with Waldenström's macroglobulinemia. To our knowledge, this is the first report to describe a possible association between distal renal tubular acidosis and Waldenström's macroglobulinemia. Our case also emphasizes the importance of prompt recognition of distal renal tubular acidosis in patients with Waldenström's macroglobulinemia because of its metabolic disturbances and potentially life threatening complications.