Preoperative alterations in correlation properties and complexity of R-R interval dynamics predict the risk of atrial fibrillation after coronary artery bypass grafting in patients with preserved left ventricular function

Introduction: We evaluated whether there are constant preoperative alterations in nonlinear R–R interval dynamics that associate with the risk of postoperative atrial fibrillation in patients with preserved left ventricular function. Methods: We analyzed mean normal‐to‐normal R–R intervals, short‐term scaling exponent of detrended fluctuation analysis (DFA α₁), approximate entropy and entropy of symbolic dynamics (SymDyn En) from 10‐minute ECG recordings during rest, paced breathing, and passive tilt performed 1 day before surgery in 67 elective coronary artery bypass grafting patients. Results: Nineteen patients developed postoperative atrial fibrillation. The preoperative DFA α₁ was constantly lower in patients developing postoperative atrial fibrillation than in patients remaining in sinus rhythm (P = 0.016); during spontaneous breathing, the DFA α₁ was 0.93 ± 0.33 in patients with atrial fibrillation and 1.13 ± 0.24 in patients with sinus rhythm. The entropy of symbolic dynamics was higher during the spontaneous breathing in patients with atrial fibrillation than in patients with sinus rhythm (4.72 ± 0.51 vs 4.36 ± 0.51, P = 0.012). Higher short‐term scaling exponent of detrended fluctuation analysis during the spontaneous breathing period reduced the risk of postoperative atrial fibrillation (OR 0.31 for an interquartile increase in DFA α₁, 95% CI 0.13–0.78), while higher entropy of symbolic dynamics increased it (OR 3.16 for an interquartile increase in SymDyn En, 95% CI 1.23–8.10), independently of age and clinical risk factors. Conclusion: The preoperatively altered nonlinear R–R interval dynamics were independent predictors of postoperative atrial fibrillation and might become a useful tool for the risk assessment of atrial fibrillation.     

Systematic Review and Meta-analysis of Circulatory Disease from Exposure to Low-Level Ionizing Radiation and Estimates of Potential Population Mortality Risks

Background: Although high doses of ionizing radiation have long been linked to circulatory disease, evidence for an association at lower exposures remains controversial. However, recent analyses suggest excess relative risks at occupational exposure levels.Objectives: We performed a systematic review and meta-analysis to summarize information on circulatory disease risks associated with moderate- and low-level whole-body ionizing radiation exposures.Methods: We conducted PubMed/ISI Thomson searches of peer-reviewed papers published since 1990 using the terms “radiation” AND “heart” AND “disease,” OR “radiation” AND “stroke,” OR “radiation” AND “circulatory” AND “disease.” Radiation exposures had to be whole-body, with a cumulative mean dose of < 0.5 Sv, or at a low dose rate (< 10 mSv/day). We estimated population risks of circulatory disease from low-level radiation exposure using excess relative risk estimates from this meta-analysis and current mortality rates for nine major developed countries.Results: Estimated excess population risks for all circulatory diseases combined ranged from 2.5%/Sv [95% confidence interval (CI): 0.8, 4.2] for France to 8.5%/Sv (95% CI: 4.0, 13.0) for Russia.Conclusions: Our review supports an association between circulatory disease mortality and low and moderate doses of ionizing radiation. Our analysis was limited by heterogeneity among studies (particularly for noncardiac end points), the possibility of uncontrolled confounding in some occupational groups by lifestyle factors, and higher dose groups (> 0.5 Sv) generally driving the observed trends. If confirmed, our findings suggest that overall radiation-related mortality is about twice that currently estimated based on estimates for cancer end points alone (which range from 4.2% to 5.6%/Sv for these populations).     

Urine albumin/creatinine ratio and echocardiographic left ventricular structure and function in hypertensive patients with electrocardiographic left ventricular hypertrophy: the LIFE study. Losartan Intervention for Endpoint Reduction

Background Albuminuria, reflecting systemic microvascular damage, and left ventricular (LV) geometric abnormalities have both been shown to predict increased cardiovascular morbidity and mortality. However, the relationship between these markers of cardiovascular damage has not been evaluated in a large hypertensive population. Methods The urine albumin/creatinine ratio (UACR) and echocardiographic measures of LV structure and function were obtained in 833 patients with stage I to III hypertension and LV hypertrophy determined by electrocardiogram (ECG) (Cornell voltage-duration or Sokolow-Lyon voltage criteria) after 14 days of placebo treatment. Results Patients' mean ages were 66 years, 42% were women, 23% had microalbuminuria, and 5% had macroalbuminuria. Patients with eccentric or concentric LV hypertrophy had higher prevalences of microalbuminuria (average 26%-30% vs 9%, P < .001) and macroalbuminuria (6%-7% vs <1%, P < .001). Furthermore, patients with microalbuminuria and macroalbuminuria had a significantly higher LV mass and lower endocardial and midwall fractional shortening. Patients with abnormal diastolic LV filling parameters had a significantly increased prevalence of microalbuminuria. In univariate analyses, UACR correlated positively to LV mass, systolic blood pressure, age (all P < .001) and pulse pressure/stroke volume and negatively to relative wall thickness (both P < .01) and endocardial (P < .05) and midwall shortening (P < .001) but not to diastolic filling parameters. In multiple regression analysis higher UACR was associated with higher LV mass (β = .169, P < .001) independently of older age (β = .095, P < .01), higher systolic pressure (β = .163), black race (β = .186), and diabetes (β = .241, all P < .001). Conclusions In hypertensive patients with ECG LV hypertrophy, abnormal LV geometry and high LV mass are associated with high UACR independent of age, systolic blood pressure, diabetes, and race, suggesting parallel cardiac and microvascular damage. (Am Heart J 2002;143:319-26.)     

Respiratory sinus arrhythmia as a predictor of sudden cardiac death after myocardial infarction

Background. Measurement of high-frequency (HF) spectral power of heart rate (HR) variability has not been able to identify the patients at risk of sudden cardiac death (SCD) despite the experimental evidence of protective role of vagal activity for fatal arrhythmias.

Aim. We developed a novel respiratory sinus arrhythmia (RSA) analysis method and tested its ability to predict SCD after an acute myocardial infarction.

Method. The RSA analysis method was developed in 13 subjects from simultaneous recordings of respiration and R-R intervals. An adaptive threshold was computed based on the zero-phase forward and reverse digital filtering in the analysis of RSA. With this method, only respiration-related R-R interval fluctuations are included. The prognostic power of RSA, analyzed from 24-hour electrocardiographic recordings, was subsequently assessed in a large postinfarction population including 1631 patients with mean follow-up of 40±17 months.

Results. Depressed RSA was a strong predictor of SCD (hazard ratio 7.4; 95% CI 3.6–15.1; P <0.0001) but only a weak predictor of non-SCD. The RSA index remained an independent predictor of SCD after adjustments for ejection fraction and other clinical risk variables (RR 4.7; 95% CI 2.28–9.85).

Conclusions. Reduced respiratory-related HR dynamics, detected by RSA index, are a specific marker of an increased risk of SCD among postinfarction patients.     

Differences in hand and foot psychomotor speed among 18 pairs of monozygotic twins discordant for lifelong vehicular driving

The purpose of this study was to examine driving as a determinant of hand and foot psychomotor reaction times. Visual simple and choice hand and foot psychomotor reaction times were measured. The occupational driving contrast was determined by an interview reviewing every job held during each subject's lifetime. Comparison was made of psychomotor speed among 18 pairs of 39- to 62-year-old monozygotic male twins discordant for lifelong occupational driving. The mean discordance was the equivalent of 16 years of full-time driving. The twins who drove more tended to have slower hand simple and choice reaction times, although only the difference in hand-choice decision time was statistically significant (32 ms, P<0.05). The drivers also had slower ipsilateral foot-choice decision times (21 ms, P<0.01), but on average they had faster reaction times in 8 of the 12 ipsilateral and contralateral foot measurements. The slightly longer decision times could be related to some general harmful effects of driving, possibly whole-body vibration. Faster foot movement times of drivers may be affected by practice effects of rapid lower-extremity movements in driving. Received: 24 September 1996 / Accepted: 30 April 1996     

Myocardial perfusion,oxidative metabolism,and free fatty acid uptake in patients with hypertrophic cardiomyopathy attributable to the Asp 175Asn mutation in the α-tropomyosin gene: A positron emission tomography study

Background  The relationship between myocardial metabolic changes and the severity of left ventricular (LV) hypertrophy in patients with hypertrophic cardiomyopathy (HCM) is largely unknown. We characterized metabolic abnormalities in patients with a genetically identical cause for HCM but with variable LV hypertrophy. Methods and Results  Eight patients with HCM attributable to the Asp175Asn mutation in the α-tropomyosin gene underwent myocardial perfusion, oxidative, and free fatty acid (FFA) metabolism measurements via positron emission tomography and oxygen 15-labeled water, carbon 11 acetate, and fluorine 14(R,S)-[18F] Fluoro-6-thia-heptadecanoic acid (18 FTHA). LV mass, work, and efficiency were assessed by echocardiography. Thirty-six healthy volunteers served as control subjects. Compared with control subjects, HCM patients had increased myocardial oxidative metabolism and FFA uptake (P<.05). However, in patients, LV mass was inversely related to global myocardial perfusion, oxidative metabolism, and FFA uptake (all P<.03), and regional wall thickness was inversely related to regional perfusion (P<.01), oxidative metabolism (P<.001), and FFA uptake (P<.01). Therefore patients with mild (LV mass less than median of 177 g) but not advanced LV hypertrophy were characterized by increased perfusion, oxidative metablism, and LV efficiency as compared with control subjects (P<.05). Conclusions  In HCM attributable to the Asp 175Asn mutation in the α-tropomyosin gene, myocardial oxidative metabolism and FFA metabolism are increased and inversely related to LV hypertrophy at both the whole heart and regional level. Increased metabolism and efficiency characterize patients with mild myocardial hypertrophy. These hypermetabolic alterations regress with advanced hypertrophy. Dis Tuunanen and Kuusisto contributed equally to this work This study was financially supported by an EVO grant (Kuopio University Hospital), as well as the Turunen Foundation, Instrumentarium Foundation, and Finish Cultural Foundation.     

Flow cytometric analysis of DNA ploidy and S-phase fraction from prostatic carcinomas: implications for prognosis and response to endocrine therapy

We analysed ploidy and S-phase fraction (SPF) from 78 paraffin-embedded primary prostatic carcinomas by DNA flow cytometry. DNA aneuploidy and above median (4.2%) SPF were both associated with high tumour grade, large size of prostate and presence of distant metastases. Both aneuploidy and high SPF (greater than 4.2%) indicated short 10-year progression-free (P = 0.01 for ploidy and P = 0.0002 for SPF), overall (P = 0.004 and P less than 0.0001) as well as prostate cancer survival (P = 0.002 and P less than 0.0001). Ten-year overall survival rate was 45% in cases with SPF below 4.2% and 0% in those with higher values, whereas the corresponding prostate cancer-specific survival rates were 80% and 11%, respectively. None of the seven tumours with SPF above 12% showed an objective response to endocrine therapy, whereas 26/49 (52%) of those with lower SPF values responded (P = 0.01). DNA ploidy, tumour grade, T-stage or M-stage did not significantly correlate with endocrine responsiveness. SPF was also the best predictor of progression free survival in patients treated hormonally. In conclusion, detection of high SPF in prostate cancer may indicate lack of hormonal responsiveness and poor prognosis.