Basal and post-exercise heart rate variability correlates with training load in endurance athletes / La variabilidad de la frecuencia cardíaca basal y posterior al ejercicio correlaciona con la carga de entrenamiento en atletas de resistencia / A variabilidade da frequência cardíaca basai e pós-exercício está correlacionada com a carga de treinamento em atletas de resistência

OBJECTIVE: Heart rate variability has been proposed as a valid method to examine the individual response to training load in endurance athletes. Thanks to this tool, the relationship between basal and post-exercise Heart rate variability measurements can be analyzed during a microcycle (one week) using straight values or their coefficients of variation. METHOD: Ten amateur endurance athletes (n = 5 men, n = 5 women) were monitored during a 7-day microcycle that included three road-cycling sessions, two running sessions and two trail-running sessions. The RR series were measured for 5 minutes upon wake up and after training, in a seating position, using a chest strap. RESULTS: Basal and post-exercise Heart rate variability measurements showed high correlation when weekly mean values were used, very similar to when coefficients of variation values were used. In women, the root mean square of successive differences (RMSSD) was: r= 0.73; RMSSD coefficients of variation (RMSSDcv) was: r= 0.66; natural logarithm (Ln) RMSSD: r= 0.68; LnRMSSDcv: r= 0.79; and in men it RMSSD was: r= 0.78; RMSSDcv: r= -0.62; LnRMSSD: r= 0.75; LnRMSSDcv: r= -0.73). CONCLUSION: the relationship between these two measurements could be useful to program the training loads of the following microcycle

OBJETIVO: La variabilidad de la frecuencia cardíaca se ha propuesto como un método válido para examinar la respuesta individual a la carga de entrenamiento en atletas de resistencia. El objetivo de este estudio fue analizar la relación entre las mediciones basales y post ejercicio durante un microciclo (una semana) utilizando valores directos o sus coeficientes de variación. MÉTODO: Se monitorizó a diez atletas aficionados de resistencia durante un microciclo de 7 días, que incluyó tres sesiones de ciclismo de ruta, dos sesiones de carrera y dos sesiones de trail running. Las series RR se midieron durante 5 minutos al despertar y después del entrenamiento, en posición sentado, utilizando una banda torácica. RESULTADOS: Las mediciones de variabilidad de la frecuencia cardíaca basales y post ejercicio mostraron una alta correlación cuando se usaron valores medios semanales, como cuando se usaron valores de los coeficientes de variación. En mujeres, la raíz cuadrada de la media de las diferencias de la suma de los cuadrados entre intervalos RR adyacentes (RMSSD) fue: r = 0.73; el coeficiente de variación (cv) de la RMSSD fue RMSSDcv: r = 0.66; el logaritmo natural (Ln) de la RMSSD (LnRMSSD) fue: r = 0.68; LnRMSSDcv: r = 0.79; y en los hombres fueron RMSSD: r = 0.78; RMSSDcv: r = -0.62; LnRMSSD: r = 0.75; LnRMSSDcv: r = -0.73. CONCLUSIONES: La relación entre estas dos mediciones podría ser útil para el programa de entrenamiento del microciclo posterior

OBJETIVO: A variação da frequência cardíaca tem sido utilizada como método de análise de respostas individuais a carga de treino em atletas de endurance. Graças a esta ferramenta, a relação entre a variação da frequência cardíaca basal e pós-exercício pode ser analisada durante um microciclo (uma semana) usando valores diretos ou seus coeficientes de variação. MÉTODO: Dez atletas de endurance amadores (n = 5 homens, n = 5 mulheres) foram monitorados durante microciclos de 7 dias que incluíram 3 sessões de ciclismo em estrada, duas sessões de corrida e duas sessões de corrida em trilha. As series de RR foram medidas durante 5 minutos depois de acordar e depois do exercício, em posição sentada, com recurso a cardiofrenquencímetros toráxicos. RESULTADOS: Os resultados mostram uma correlação alta entre as medidas de variação de frequência cardíaca basal e pós-exercício quando utilizados valores médios semanais, muito semelhantes aos resultados quando utilizados coeficientes de variação. Nas mulheres, a raiz quadrada media das diferenças sucessivas (RMSSD) foi: r= 0.73; coeficientes de variação RMSSD, (RMSSDcv) foi: r= 0.66; logaritmo natural (Ln) RMSSD: r = 0.68; LnRMSSDcv: r= 0.79; e nos homens, raiz quadrada media das diferenças sucessivas r= 0.78; RMSSDcv: r= -0.62; LnRMSSD: r= 0.75; LnRMSSDcv: r= -0.73). CONCLUSÃO: a relação entre estas duas medidas poderia ser útil para prescrição de cargas de treino dos microciclos seguintes

The effect of preoperative depression and anxiety on heart rate variability in women with breast cancer.

BACKGROUND: Anxiety and depression are prevalent in women with breast cancer. These can affect their autonomic nervous system and hemodynamic stability, which are important factors during operation. We aimed to assess the effect of anxiety and depression on heart rate variability (HRV) in patients with breast cancer. METHODS: Forty-nine women with breast cancer, scheduled for surgery, were asked to complete depression and anxiety questionnaires and categorized into depressed/non-depressed and anxious/non-anxious groups. Their electrocardiography (EKG) were assessed for 150 s on admission, before, and after induction of anesthesia for the presence, frequency, and range of HRV. Patients' blood pressure (BP) and HR were recorded, and normal unit high frequency (nuHF), normal unit low frequency (nuLF), LF/HF ratio, HRV index, and systolic and diastolic BP were compared between the groups in three intervals. RESULTS: Anxious and depressed groups had a significantly higher systolic, diastolic, and mean BP before and after induction and higher nuLF before induction, while the changes in nuLF, LF/HF ratio, and HRV index were not significant. Both groups with and without mood disorders had increased BP and HR before induction, which decreased after induction (P < 0.001). Decreased mean BP after induction was associated with anxiety (P < 0.05). CONCLUSION: According to the results of this study, patients with depression had less HRV in the operating theater, than the non-depressed group. After induction of anesthesia, the decrease in BP was associated with anxiety, while BP of the depressed group was higher than the non-depressed group at all intervals.

Pulse Rate Variability in Emergency Physicians During Shifts: Pilot Cross-Sectional Study.

BACKGROUND: The high prevalence of physician burnout, particularly in emergency medicine, has garnered national attention in recent years. Objective means of measuring stress while at work can facilitate research into stress reduction interventions, and wearable photoplethysmography (PPG) technology has been proposed as a potential solution. However, the use of low-burden wearable biosensors to study training and clinical practice among emergency physicians (EP) remains untested. OBJECTIVE: This pilot study aimed to (1) determine the feasibility of recording on-shift photoplethysmographic data from EP, (2) assess the quality of these data, and (3) calculate standard pulse rate variability (PRV) metrics from the acquired dataset and examine patterns in these variables over the course of an academic year. METHODS: A total of 21 EP wore PPG biosensors on their wrists during clinical work in the emergency department during a 9-hour shift. Recordings were collected during the first quarter of the academic year, then again during the fourth quarter of the same year for comparison. The overall rate of usable data collection per time was computed. Standard pulse rate (PR) and PRV metrics from these two time points were calculated and entered into Student t tests. RESULTS: More than 400 hours of data were entered into these analyses. Interpretable data were captured during 8.54% of the total recording time overall. In the fourth quarter of the academic year compared with the first quarter, there was no significant difference in median PR (75.8 vs 76.8; P=.57), mean R-R interval (0.81 vs 0.80; P=.32), SD of R-R interval (0.11 vs 0.11; P=.93), root mean square of successive difference of R-R interval (0.81 vs 0.80; P=.96), low-frequency power (3.5×103 vs 3.4×103; P=.79), high-frequency power (8.5×103 vs 8.3×103; P=.91), or low-frequency to high-frequency ratio (0.42 vs 0.41; P=.43), respectively. Power estimates for each of these tests exceeded .90. A secondary analysis of the resident-only subgroup similarly showed no significant differences over time, despite power estimates greater than .80. CONCLUSIONS: Although the use of PPG biosensors to record real-time physiological data from EP while providing clinical care seems operationally feasible, this study fails to support the notion that such an approach can efficiently provide reliable estimates of metrics of interest. No significant differences in PR or PRV metrics were found at the end of the year compared with the beginning. Although these methods may offer useful applications to other domains, it may currently have limited utility in the contexts of physician training and wellness.

Heart Rate Measures From Wrist-Worn Activity Trackers in a Laboratory and Free-Living Setting: Validation Study.

BACKGROUND: Wrist-worn activity trackers are popular, and an increasing number of these devices are equipped with heart rate (HR) measurement capabilities. However, the validity of HR data obtained from such trackers has not been thoroughly assessed outside the laboratory setting. OBJECTIVE: This study aimed to investigate the validity of HR measures of a high-cost consumer-based tracker (Polar A370) and a low-cost tracker (Tempo HR) in the laboratory and free-living settings. METHODS: Participants underwent a laboratory-based cycling protocol while wearing the two trackers and the chest-strapped Polar H10, which acted as criterion. Participants also wore the devices throughout the waking hours of the following day during which they were required to conduct at least one 10-min bout of moderate-to-vigorous physical activity (MVPA) to ensure variability in the HR signal. We extracted 10-second values from all devices and time-matched HR data from the trackers with those from the Polar H10. We calculated intraclass correlation coefficients (ICCs), mean absolute errors, and mean absolute percentage errors (MAPEs) between the criterion and the trackers. We constructed decile plots that compared HR data from Tempo HR and Polar A370 with criterion measures across intensity deciles. We investigated how many HR data points within the MVPA zone (≥64% of maximum HR) were detected by the trackers. RESULTS: Of the 57 people screened, 55 joined the study (mean age 30.5 [SD 9.8] years). Tempo HR showed moderate agreement and large errors (laboratory: ICC 0.51 and MAPE 13.00%; free-living: ICC 0.71 and MAPE 10.20%). Polar A370 showed moderate-to-strong agreement and small errors (laboratory: ICC 0.73 and MAPE 6.40%; free-living: ICC 0.83 and MAPE 7.10%). Decile plots indicated increasing differences between Tempo HR and the criterion as HRs increased. Such trend was less pronounced when considering the Polar A370 HR data. Tempo HR identified 62.13% (1872/3013) and 54.27% (5717/10,535) of all MVPA time points in the laboratory phase and free-living phase, respectively. Polar A370 detected 81.09% (2273/2803) and 83.55% (9323/11,158) of all MVPA time points in the laboratory phase and free-living phase, respectively. CONCLUSIONS: HR data from the examined wrist-worn trackers were reasonably accurate in both the settings, with the Polar A370 showing stronger agreement with the Polar H10 and smaller errors. Inaccuracies increased with increasing HRs; this was pronounced for Tempo HR.

Impact of atrial fibrillation awareness campaigns: interrupted time series using the Clinical Practice Research Datalink.

Aim: This study investigated whether the rates of atrial fibrillation (AF) consultations changed following AF awareness campaigns in England. Materials & methods: Among adults in the Clinical Practice Research Datalink, Poisson regression was used to model weekly rates of AF-related consultations over time. The models were used to assess whether rates changed in the 8 weeks following World Heart Rhythm Week (WHRW) and Global AF aware week. Results: A higher incidence of pulse checks was observed following WHRW (IRR 1.16 [95% CI 1.08-1.24]). No difference in the incidence of AF diagnoses was noted following WHRW (IRR: 1.03 [95% CI: 0.97-1.09]) or Global AF aware week (IRR: 0.94 [95% CI: 0.88-1.00]). Conclusion: The results suggest AF campaigns may increase awareness but do not bring about short-term increases in the rates of AF diagnoses.

Validation of Polar OH1 optical heart rate sensor for moderate and high intensity physical activities.

BACKGROUND: Optical measurement techniques and recent advances in wearable technology have made heart rate (HR) sensing simpler and more affordable. OBJECTIVES: The Polar OH1 is an arm worn optical heart rate monitor. The objectives of this study are two-fold; 1) to validate the OH1 optical HR sensor with the gold standard of HR measurement, electrocardiography (ECG), over a range of moderate to high intensity physical activities, 2) to validate wearing the OH1 at the temple as an alternative location to its recommended wearing location around the forearm and upper arm. METHODS: Twenty-four individuals participated in a physical exercise protocol, by walking on a treadmill and riding a stationary spin bike at different speeds while the criterion measure, ECG and Polar OH1 HR were recorded simultaneously at three different body locations; forearm, upper arm and the temple. Time synchronised HR data points were compared using Bland-Altman analyses and intraclass correlation. RESULTS: The intraclass correlation between the ECG and Polar OH1, for the aggregated data, was 0.99 and the estimated mean bias ranged 0.27-0.33 bpm for the sensor locations. The three sensors exhibited a 95% limit of agreement (LoA: forearm 5.22, -4.68 bpm; upper arm 5.15, -4.49; temple 5.22, -4.66). The mean of the ECG HR for the aggregated data was 112.15 ± 24.52 bpm. The intraclass correlation of HR values below and above this mean were 0.98 and 0.99 respectively. The reported mean bias ranged 0.38-0.47 bpm (95% LoA: forearm 6.14, -5.38 bpm; upper arm 6.07, -5.13 bpm; temple 6.09, -5.31 bpm), and 0.15-0.16 bpm (95% LoA: forearm 3.99, -3.69 bpm; upper arm 3.90, -3.58 bpm; temple 4.06, -3.76 bpm) respectively. During different exercise intensities, the intraclass correlation ranged 0.95-0.99 for the three sensor locations. During the entire protocol, the estimated mean bias was in the range -0.15-0.55 bpm, 0.01-0.53 bpm and -0.37-0.48 bpm, for the forearm, upper arm and temple locations respectively. The corresponding upper limits of 95% LoA were 3.22-7.03 bpm, 3.25-6.82 bpm and 3.18-7.04 bpm while the lower limits of 95% LoA were -6.36-(-2.35) bpm, -6.46-(-2.30) bpm and -7.42-(-2.41) bpm. CONCLUSION: Polar OH1 demonstrates high level of agreement with the criterion measure ECG HR, thus can be used as a valid measure of HR in lab and field settings during moderate and high intensity physical activities.

Accuracy of Apple Watch Measurements for Heart Rate and Energy Expenditure in Patients With Cardiovascular Disease: Cross-Sectional Study.

BACKGROUND: Wrist-worn tracking devices such as the Apple Watch are becoming more integrated in health care. However, validation studies of these consumer devices remain scarce. OBJECTIVES: This study aimed to assess if mobile health technology can be used for monitoring home-based exercise in future cardiac rehabilitation programs. The purpose was to determine the accuracy of the Apple Watch in measuring heart rate (HR) and estimating energy expenditure (EE) during a cardiopulmonary exercise test (CPET) in patients with cardiovascular disease. METHODS: Forty patients (mean age 61.9 [SD 15.2] yrs, 80% male) with cardiovascular disease (70% ischemic, 22.5% valvular, 7.5% other) completed a graded maximal CPET on a cycle ergometer while wearing an Apple Watch. A 12-lead electrocardiogram (ECG) was used to measure HR; indirect calorimetry was used for EE. HR was analyzed at three levels of intensity (seated rest, HR1; moderate intensity, HR2; maximal performance, HR3) for 30 seconds. The EE of the entire test was used. Bias or mean difference (MD), standard deviation of difference (SDD), limits of agreement (LoA), mean absolute error (MAE), mean absolute percentage error (MAPE), and intraclass correlation coefficients (ICCs) were calculated. Bland-Altman plots and scatterplots were constructed. RESULTS: SDD for HR1, HR2, and HR3 was 12.4, 16.2, and 12.0 bpm, respectively. Bias and LoA (lower, upper LoA) were 3.61 (-20.74, 27.96) for HR1, 0.91 (-30.82, 32.63) for HR2, and -1.82 (-25.27, 21.63) for HR3. MAE was 6.34 for HR1, 7.55 for HR2, and 6.90 for HR3. MAPE was 10.69% for HR1, 9.20% for HR2, and 6.33% for HR3. ICC was 0.729 (P<.001) for HR1, 0.828 (P<.001) for HR2, and 0.958 (P<.001) for HR3. Bland-Altman plots and scatterplots showed good correlation without systematic error when comparing Apple Watch with ECG measurements. SDD for EE was 17.5 kcal. Bias and LoA were 30.47 (-3.80, 64.74). MAE was 30.77; MAPE was 114.72%. ICC for EE was 0.797 (P<.001). The Bland-Altman plot and a scatterplot directly comparing Apple Watch and indirect calorimetry showed systematic bias with an overestimation of EE by the Apple Watch. CONCLUSIONS: In patients with cardiovascular disease, the Apple Watch measures HR with clinically acceptable accuracy during exercise. If confirmed, it might be considered safe to incorporate the Apple Watch in HR-guided training programs in the setting of cardiac rehabilitation. At this moment, however, it is too early to recommend the Apple Watch for cardiac rehabilitation. Also, the Apple Watch systematically overestimates EE in this group of patients. Caution might therefore be warranted when using the Apple Watch for measuring EE.

Fetal cardiac time intervals in healthy pregnancies - an observational study by fetal ECG (Monica Healthcare System).

BACKGROUND: Fetal electrocardiogram (fECG) can detect QRS signals in fetuses from as early as 17 weeks' gestation; however, the technique is limited by the minute size of the fetal signal relative to noise ratio. The aim of this study was to evaluate precise fetal cardiac time intervals (fCTIs) with the help of a newly developed fetal ECG device (Monica Healthcare System). METHODS: In a prospective manner we included 15-18 healthy fetuses per gestational week from 32 weeks onwards. The small and wearable Monica AN24 monitoring system uses standard ECG electrodes placed on the maternal abdomen to monitor fECG, maternal ECG and uterine electromyogram (EMG). Fetal CTIs were estimated on 1000 averaged fetal heart beats. Detection was deemed successful if there was a global signal loss of less than 30% and an analysis loss of the Monica AN24 signal separation analysis of less than 50%. Fetal CTIs were determined visually by three independent measurements. RESULTS: A total of 149 fECGs were performed. After applying the requirements 117 fECGs remained for CTI analysis. While the onset and termination of P-wave and QRS-complex could be easily identified in most ECG patterns (97% for P-wave, PQ and PR interval and 100% for QRS-complex), the T-wave was detectable in only 41% of the datasets. The CTI results were comparable to other available methods such as fetal magnetocardiography (fMCG). CONCLUSIONS: Although limited and preclinical in its use, fECG (Monica Healthcare System) could be an additional useful tool to detect precise fCTIs from 32 weeks' gestational age onwards.

Validation of a new algorithm for the short-term variation of the fetal heart rate: an antepartum prospective study.

AIMS: Currently one of the most widespread systems for the computerized analysis of the fetal heart rate (FHR) is the Dawes-Redman system, where the short-term variation (STV) of the FHR is measured by dividing each minute into 16 segments (STV16). Technical progress has allowed for the development of a new algorithm, which measures the STV by dividing each minute into 240 segments (STV240), thus approximating the beat-to-beat variation. The STV240 still lacks reference values. Our aim was to develop clinically relevant reference values for the STV240 and compare them to the ones for the STV16. METHODS: In a single centre, observational study, a total of 228 cardiotocograms were registered and subsequently analyzed with both algorithms (STV240 and STV16). RESULTS: The 95% confidence interval (CI) was calculated for both algorithms. The values of the STV240 were significantly lower in comparison to the ones of the STV16. Not only the mean values but also the 95th percentile of the STV240 lay beneath the existent cut-off value for the STV16. CONCLUSIONS: Every clinician using the new algorithm must be aware that the normal values for the STV240 lie beneath the, up until now, established cut-off values for the STV16.

A Device Histogram-Based Simple Predictor of Mortality Risk in ICD and CRT-D Patients: The Heart Rate Score.

BACKGROUND: We hypothesized that survival in implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) patients is predicted by baseline Heart Rate Score. METHODS: Heart Rate Score is determined from the atrial paced and sensed histogram of a DDD ICD or CRT-D, and defined as percent of beats in the histogram in the tallest 10 beats/min range bin. It was calculated at initial remote monitoring for patients enrolled in LATITUDE® without persistent atrial fibrillation, and with pulse generators implanted in 2006-2011. Univariate, multivariate, and Kaplan-Meier analyses determined the impact of Heart Rate Score on survival. RESULTS: Of 57,893 ICDs and 67,929 CRT-Ds followed for 2.4 ± 1.5 years, each 10% increase in Heart Rate Score was associated with decreased survival (CRT-D hazard ratio [HR] 1.07 95%, confidence interval 1.06-1.07, P < 0.0001; ICD HR 1.05, 95% confidence interval 1.04-1.06, P < 0.0001). Multivariate analysis showed survival decreased with increasing age, atrial fibrillation, presence of a shock in first-year follow-up, and increasing programmed lower pacing rate in ICD and CRT-D patients. Increased percent right ventricular pacing predicted mortality in ICD patients, while male gender and lower percent left ventricular pacing predicted mortality in CRT patients. Heart Rate Score predicted survival independent of those variables. Heart Rate Score correlates with heart rate variability (standard deviation of average R-R intervals [SDANN]) when both are obtainable, but SDANN was only present in 6% of patients with Heart Rate Score >70%. CONCLUSION: A simple device histogram measure, Heart Rate Score, predicts survival in ICD and CRT-D patients independent of the available variables, and even when SDANN is unavailable.

Usefulness of measurement of heart rate variability by holter ECG in hemodialysis patients.

BACKGROUND: Major adverse cardiac and cerebrovascular event (MACCE) is one of most common complications of hemodialysis patients. Heart rate variability (HRV) is the predictor of death in heart disease patients. However, there are no studies on the role of HRV in hemodialysis patients. METHODS: From September 2009 to March 2011, 24-h electrocardiography was performed in 101 hemodialysis patients. Standard deviation of sequential 5-minute N-N interval means (SDANN) and standard deviation of the N-N interval (SDNN) was examined by a 24-h ECG analysis. Patients were observed prospectively. The primary endpoints were incidence of MACCE and MACCE-free survival. RESULTS: We studied 90 hemodialysis patients (64 males, 63.4 ± 11.8 years old). During a follow-up period of 32.0 ± 11.7 months, 33 patients developed MACCE. 24-h ECG showed mean SDNN 93.4 ± 33.4 ms and mean SDANN 83.2 ± 31.3 ms. MACCE group showed significantly lower SDNN and SDANN than event-free group. In Kaplan-Meier analysis higher SDNN and SDANN group showed significantly higher event-free survival rate than lower group. Using a Cox proportional hazards model, SDNN was independent prognostic factor while SDANN or diabetic status was not significant. In diabetic cases, there were no differences in any factors for the incidence of MACCE between higher SDNN, SDANN groups and lower groups. On the other hand in non-diabetic cases, lower SDNN or SDANN group developed significantly higher MACCE than higher groups. CONCLUSION: Measurement of HRV by Holter ECG is useful to predict MACCE in hemodialysis patients, especially non-diabetic group.

Intersubject variability and intrasubject reproducibility of 12-lead ECG metrics: Implications for human verification.

BACKGROUND: Electrocardiogram (ECG) biometrics is an advanced technology, not yet covered by guidelines on criteria, features and leads for maximal authentication accuracy. OBJECTIVE: This study aims to define the minimal set of morphological metrics in 12-lead ECG by optimization towards high reliability and security, and validation in a person verification model across a large population. METHODS: A standard 12-lead resting ECG database from 574 non-cardiac patients with two remote recordings (>1year apart) was used. A commercial ECG analysis module (Schiller AG) measured 202 morphological features, including lead-specific amplitudes, durations, ST-metrics, and axes. Coefficient of variation (CV, intersubject variability) and percent-mean-absolute-difference (PMAD, intrasubject reproducibility) defined the optimization (PMAD/CV→min) and restriction (CV<30%) criteria for selection of the most stable and distinctive features. Linear discriminant analysis (LDA) validated the non-redundant feature set for person verification. RESULTS AND CONCLUSIONS: Maximal LDA verification sensitivity (85.3%) and specificity (86.4%) were validated for 11 optimal features: R-amplitude (I,II,V1,V2,V3,V5), S-amplitude (V1,V2), Tnegative-amplitude (aVR), and R-duration (aVF,V1).

Reference ranges for short-term heart rate variability measures in individuals free of cardiovascular disease: The Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: Normative values for heart rate variability (HRV) measures from 10-s electrocardiograms (ECG) have not been defined. METHODS: We reported borderline abnormal (<5th percentile) and abnormal (<2nd percentile) values of standard deviation of all normal-to-normal R-R intervals (SDNN) and root mean square of successive differences between normal-to-normal R-R intervals (rMSSD) from 10-s ECGs in 1175 participants (mean age=59±10; 59% female; 47% white) ≥45years of age from the Multi-Ethnic Study of Atherosclerosis (MESA) who were free of cardiovascular disease (CVD) and CVD risk factors. We validated the prognostic significance of these measures in a subset of the MESA cohort with complete data. RESULTS: Borderline abnormal and abnormal SDNN and rMSSD varied by sex and race. Borderline abnormal and abnormal SDNN and rMSSD were associated with an increased risk of CVD and all-cause mortality. CONCLUSIONS: The references ranges provided in this report will guide future research using these common HRV parameters.

Three dimensional left atrial volume index is correlated with P wave dispersion in elderly patients with sinus rhythm.

BACKGROUND: P wave dispersion is a noninvasive electrocardiographic predictor for atrial fibrillation. The aim of the study was to explore relation between left atrial volume index assessed by 3-dimensional echocardiography and P wave dispersion in elderly patients. METHODS: Seventy-three consecutive patients over the age of 65 (mean age: 75 ± 7 years, 17 men) were included. P wave dispersion is calculated as the difference between maximum and minimum P wave durations. Left atrial volume index was measured by both 2-dimensional and 3-dimensional echocardiography and categorized as normal (≤ 34 mL/m(2)) or increased (mild, 35-41 mL/m(2); moderate, 42-48 mL/m(2); severe, ≥ 49 mL/m(2)). RESULTS: Thirty-one patients had normal left atrium while 24 patients had mildly enlarged, nine had moderately enlarged, and nine had severely enlarged left atrium. Prolongation of P wave dispersion was more prevalent in patients with dilated left atrium. P wave dispersion was significantly correlated with both 2-dimensional (r = 0.600, p < 0.001) and 3-dimensional left atrial volume index (r = 0.688, p < 0.001). Both left atrial volume indexes were associated with prolonged P wave dispersion when adjusted for age, sex, presence of hypertension, and left ventricular mass index. Receiver-operator characteristic (ROC) analysis revealed that a 3-dimensional left atrial volume index ≥ 25 mL/m(2) separated patients with prolonged P wave dispersion with a sensitivity of 82.2 %, specificity of 67.9 %, positive predictive value of 80.4 %, and negative predictive value of 70.4 %. CONCLUSION: In elderly patients, 3-dimensional left atrial volume index showed a better correlation with P wave dispersion and might be helpful in discriminating patients with prolonged P wave dispersion, who might be prone to atrial fibrillation.

Admission heart rate in relation to presentation and prognosis in patients with acute myocardial infarction. Treatment regimens in German chest pain units.

BACKGROUND: Higher heart rates on admission have been associated with poor outcomes in patients with an acute coronary syndrome in previous cohorts. Whether such a linear relationship still exists in contemporary high-level care is unclear. METHODS: Prospectively collected data from patients presenting with myocardial infarction (MI) in centers participating in the Chest Pain Unit (CPU) Registry between December 2008 and July 2014 were analyzed. Patients were classified according to their initial heart rate (I: < 50; II: 50-69; III: 70-89; IV: ≥ 90 bpm). A total of 6,168 patients out of 30,339 patients presenting to 38 centers were included in the study. RESULTS: Patients in group IV had more comorbidities, while patients in group I more often had a history of MI. Patients in the lowest heart rate group presented significantly earlier to the hospital (4 h 31 min vs. 7 h 37 min; p < 0.05) and had the highest rate of interventions. The overall survival after 3 months was significantly worse in group IV after adjusting for baseline variables. In the subgroup analysis, heart rate was a prognostic factor in the non-ST-segment elevation MI group but not in the ST-segment elevation MI group. The correlation between heart rate and major adverse cardiac events followed a J-shaped curve with worst outcomes in the lowest and highest heart rate groups. CONCLUSION: Patients admitted to a dedicated CPU with the diagnosis of MI and a heart rate > 90 bpm experience reduced survival at 3 months despite optimal treatment. Patients with bradycardia also seem to be at increased risk for cardiovascular events despite much earlier presentation and treatment.

Prognostic value of heart rate response during regadenoson stress myocardial perfusion imaging in patients with end stage renal disease.

BACKGROUND: Blunted heart rate response (HRR) to vasodilator stress agents is associated with worse outcomes. There are limited data assessing the effect of impaired HRR to regadenoson among patients with end-stage renal disease (ESRD) undergoing stress myocardial perfusion imaging (MPI). METHODS: We prospectively followed patients with ESRD enrolled in the ASSUAGE and ASSUAGE-CKD trials. HRR was defined as 100*(peak stress heart rate-resting heart rate)/resting heart rate. Study cohort was dichotomized to blunted and normal HRR groups according to an established median HRR value <28% or ≥28%, which were propensity-score matched based on 22 clinical and imaging covariates. The Primary endpoint was all-cause death. The secondary cardiac-specific endpoints included: (1) the composite endpoint of cardiac death or myocardial infarction; (2) the composite endpoint of cardiac death, myocardial infarction, or late (>90 days) coronary revascularization. RESULTS: There were 303 patients followed for 35 ± 10 months. In the entire cohort, there was a stepwise increase in the rates of death and all secondary endpoints with worsening HRR (P values ≤.001). Blunted HRR (<28%) was associated with increased risk of death (unadjusted hazard ratio 4.10 [1.98-8.46], P < .001) and all secondary endpoints (P ≤ .001). After multivariate adjustment, HRR remained an independent predictor of mortality and secondary endpoints whether used as continuous or dichotomous variable, and added incremental prognostic value for all-cause death (P = .046). Blunted HRR was associated with increased event rate among patients with normal myocardial perfusion (P = .001) and abnormal perfusion (P = .053). In the propensity-matched cohort of 132 patients (66 in each group), blunted HRR was associated with significant increase in all-cause death (21% vs. 5%, HR 5.09 [1.46-17.7], P=.011), and similarly for the secondary endpoints. CONCLUSION: Blunted HRR (<28%) to regadenoson is a strong and independent predictor of death and cardiovascular events in patients with ESRD and adds incremental prognostic value.