Are heart rate monitors valuable tools for diagnosing arrhythmias in endurance athletes?

Millions of physically active individuals worldwide use heart rate monitors (HRM s) to control their exercise intensity. In many cases, the HRM indicates an unusually high heart rate (HR ) or even arrhythmias during training. Unfortunately, studies assessing the reliability of these devices to help control HR disturbances during exercise do not exist. We examined 142 regularly training endurance runners and cyclists, aged 18‐51 years, with unexplained HR abnormalities indicated by various HRM s to assess the utility of HRM s in diagnosing exertion‐induced arrhythmias. Each athlete simultaneously wore a Holter electrocardiogram (ECG ) recorder and an HRM during typical endurance training in which they had previously detected “arrhythmias” to verify the diagnosis. Average HR s during exercise were precisely recorded by all types of HRM s. No signs of arrhythmia were detected during exercise in approximately 39% of athletes, and concordant HR s were recorded by the HRM s and Holter ECG . HRM s indicated surprisingly high short‐term HR s in 45% of athletes that were not detected by the Holter ECG and were artifacts. In 15% of athletes, single ventricular/supraventricular beats were detected by the Holter ECG but not by the HRM . We detected a serious tachyarrhythmia in the HRM and Holter ECG data with concomitant clinical symptoms in only one athlete, who was forced to cease exercising. We conclude that the HRM is not a suitable tool for monitoring heart arrhythmias in athletes and propose an algorithm to exclude the suspicion of exercise‐induced arrhythmia detected by HRM s in asymptomatic, physically active individuals.     

Safety of air travel following acute myocardial infarction

BACKGROUND: A randomized, single-blind, controlled trial was carried out to: 1) examine the safety of patients flying on commercial airlines 2 wk after a myocardial infarction; 2) determine whether or not the use of supplemental oxygen was associated with a reduced risk of in-flight adverse events; and 3) determine the need for a medical escort. METHODS: There were 38 patients who were prospectively and randomly assigned supplemental continuous oxygen therapy (2 L x min(-1) via nasal prongs; n = 19) or no oxygen (n = 19) during the flight. Prior to flying, an escorting doctor completed a medical questionnaire for each patient. Both groups underwent Holter monitoring throughout the flight. The major end-point was the development of inflight myocardial ischemia, as detected by Holter monitoring. Minor end-points included patients complaining of chest pain or dyspnea; the detection of bigeminy or trigeminy by Holter monitoring; or oxygen desaturation to less than 90%, as measured by pulse oximetry. RESULTS: Of the 38 patients enrolled, there was only 1 major end-point. This patient had a brief, self-limiting, asymptomatic episode of myocardial ischemia diagnosed by Holter monitoring. Minor end-points occurred in 13 (34%) patients. One patient had asymptomatic evidence of S-T depression on a transport monitor, but not on the Holter. Five patients had transient low (<90%) oxygen saturations, two complained of chest pain, and five had complex ventricular ectopic beats or periods of transient ventricular tachycardia. None of the minor end-points were associated with Holter evidence of myocardial ischemia. Of the 30 patients with completed questionnaires and Holter results, there was no difference in the incidence of minor end-points between the oxygen (5/13) and no oxygen groups (6/15) (p = 0.93). Intervention by the medical escort consisted of commencing oxygen therapy on those patients with low oxygen saturations and those with chest pain. Use of an already dispensed glyceryl trinitrate spray was initiated in one patient with chest pain that turned out to be non-ischemic when the Holter traces were later analyzed. CONCLUSIONS: This study suggests that, provided that care is taken during the immediate preflight and postflight phases not to overexert the patients, neither supplemental oxygen nor medical escorts are needed in the transportation of patients who fly 2 wk after acute myocardial infarction.     

Effect of impact stresses on the rat heart and hemodynamics]

An experimental impact on the rat chest in the cardiac area induced bradycardia, arrhythmia, ectopic beats, atrio-ventricular blockade that was followed by a fall of the arterial pressure and a rise in the venous pressure, a decrease of the cardiac output and blood volume. Breakages in cardiac myofibers were seen under the microscope. These changes can be brought about by a direct effect of impact accelerations on the heart. It is concluded that tolerance of the animal heart to impact accelerations is limited by bradycardia, arterial pressure fall and a 25% decrease of the cardiac output. Greater effects may produce breakages in myofibers. An active alertness and unloading of the right atrium increase the heart tolerance to impact accelerations and potassium chloride prevents hazardous cardiac arrhythmias.     

Biomagnetic localization of ventricular arrhythmias.

The magnetic fields caused by electrical activity of the human heart can be coherently measured with a highly sensitive, multichannel, superconducting quantum interference-device system and can enable noninvasive localization of the underlying electrical activity. The magnetocardiograms (MCGs) of 10 patients with spontaneous premature ventricular complexes (PVCs), three patients with ventricular tachycardia (VT), and four healthy subjects with induced paced beats were recorded for 2-15 minutes. After correction for superimposed repolarization activity, the site of origin of the arrhythmias was localized from the magnetic field distribution at the onset of the ectopic beats. The localization results of paced beats showed an error of a few millimeters in relation to the position of the catheter tip. The results of spontaneous PVC and VT were confirmed with endocardial mapping or associated with ischemic lesions. The authors conclude that multichannel magnetocardiographic studies enable the completely noninvasive localization of ventricular arrhythmias.     

Holter monitor findings in asymptomatic male military aviators without structural heart disease

PURPOSE: Our study was designed to determine the spectrum of Holter monitor findings in normal male military aviators to establish a reference for aircrew populations with cardiac related diagnoses. METHODS: We identified all individuals with normal cardiac catheterization in the United States Air Force Aeromedical Consultation Service cardiac catheterization database from January 1984 to December 1998. Cases with valvular disease, left or right bundle branch block, and referral diagnoses of ectopy or arrhythmia were then excluded. Results of Holter monitor studies performed on the remaining aviators prior to cardiac catheterization were then collected and tabulated. Frequency of isolated ectopy was classified as a percentage of the total beats on the Holter monitor: rare (< or =0.1%), occasional (>0.1 to 1.0%), frequent (>1.0 to 10%) and very frequent (>10%). RESULTS: From 1575 consecutive cardiac catheterizations reviewed, 303 aviators met the above inclusion criteria. Only 36 of 303 (11.9%) had no ectopy at all. Rare, occasional, frequent and very frequent isolated atrial ectopy occurred in 72.9%, 2.6%, 2.3% and 0.3%, respectively. The same categories of isolated ventricular ectopy occurred in 40.9%, 7.9%, 3.3% and 0.0%. Atrial and ventricular pairs occurred in 14.5% and 4.3%, respectively. Nonsustained supraventricular and ventricular tachycardia (duration 3 to 10 beats) occurred in 4.3% (13/303) and 0.7% (2/303), respectively. There were no sustained supraventricular or ventricular tachycardias. CONCLUSIONS: In this population, absence of ectopy is unusual while rare isolated ectopy is common. These findings may help define the aeromedical/clinical significance of Holter monitors performed on aircrew with underlying cardiac complaints or diagnoses.     

Therapeutic effects of oral dipyridamole on myocardial perfusion and left ventricular function in patients with hypertrophic cardiomyopathy

As myocardial ischemia possibly due to small vessel coronary disease has been reported in hypertrophic cardiomyopathy (HCM), we investigated therapeutic efficacy of oral dipyridamole (DP) in 20 patients. DP of 150 mg/day for 2 weeks significantly increased septal washout rate (39 +/- 14 to 45 +/- 11%) in exercise Tl-201 myocardial imaging, improving reversible defects in 6 patients. The result further supported that small vessel coronary disease could induce myocardial ischemia in HCM. In RI angiography. DP increased ejection fraction (50 +/- 9 to 53 +/- 7%) and peak filling rate (1.9 +/- 0.6 to 2.0 +/- 0.5 sec-1) at rest. DP also improved subjective symptoms, cardiac size and atrial premature beats in Holter monitoring. In exercise test, maximal work load was increased from 7.6 +/- 2.0 to 8.3 +/- 1.4 METS. These observations indicate that oral DP is an useful drug for treatment of HCM, in improving subjective symptoms, left ventricular function, exercise tolerance and arrhythmias, possibly due to beneficial effects on myocardial perfusion and afterload reduction.     

Informative value of the studies of beta 2-microglobulin in the plasma and urine of humans for evaluation of the resistance to static and bicycle ergometry tests]

Changes of the beta 2-microglobulin concentration in blood and urine were measured in response to static and bicycle ergometry tests. In both cases, the concentration of beta 2-microglobulin in urine increased. A higher level of its renal excretion was seen in stable subjects before and after the tests. This relationship was also seen in patients with neurocirculatory dystonia of the hypertensive type. Possible mechanisms of these reactions are discussed.     

高原环境下飞行员的心血管功能测定

为观察高原飞行训练对心血管功能的影响，对进驻海拔3600m高原进行飞行训练3个月的10名飞行员进行了13项心血管功能指标及动态和常规心电图测定，并与同期进入高原的10名地勤人员及10名驻平原地区的飞行员作对照研究。结果表明：①除高原飞行员的有效血容量（BV）低于平原飞行员（P＜0．05）外,3组人员其余12项心功能招数之间均免显著差异；②24hHolier监测显示，高原飞行员24h平均心率、最高心率及最低心率与高原地勤人员及平原飞行员基本一致。除实性心动过速、过缓外，高原飞行员中有房性早搏者8人，室性早搏3人，均＜100次／24h或＜1次／1000心搏，为偶发早搏，无重要临床意义；③常规心电图表现，高原飞行员与其他两组人员基本一致。提示：飞行员在高原训练3个月中，心血管功能无显著改变。     

Delta-sleep peptide as a modulator of cardiac activity: theoretical recommendations for practice

In acute and chronic animal (rabbits, rats) experiments it has been shown that delta-sleep producing peptide (DSPP) exerts a noticeable effect on the cardiac function and regulation. DSPP at a dose of 60 nm/kg can prolong the effects of vagus and inhibit those of sympathetic nerves on the cardiac function and, consequently, can influence the function of choline- and adrenergic transmitters. DSPP blocks pressor vascular reactions in response to direct electrical stimulation of ventromedian hypothalamus and thus increases the survival of animals exposed to an acute emotional stress. DSPP normalizes the electrical stability of the heart and produces an antiarrhythmic effect on ventricular ectopic beats that occur in response to emotional stresses. In view of this, DSPP can be recommended for clinical trials as a drug preventing cardiac arrhythmias in stressful situations.     

青山健心片抗过早搏动的临床研究

目的　研究青山健心片对过早搏动的临床疗效及作用机制。方法　将过早搏动患者 60例随机分为两组 :治疗组 3 0例 ,青山健心片治疗 ,对照组 3 0例 ,心律宁片治疗 ,疗程 3 0d。观察两组常规心电图、动态心电图、证候、症状、舌象、脉象等变化。结果　治疗组在常规心电图、动态心电图的早搏变化及证候、症状、舌象、脉象等方面的治疗效果均优于对照组 (P <0 .0 5 )。结论　青山健心片具有良好的抗过早搏动的作用。     

Complex ventricular arrhythmia induced by overuse of potassium supplementation in a young male football player. Case report

People practising regular physical activity usually drink hydrosaline beverages. In this study is reported the case of a young football player suffering from premature ventricular beats. He used to take regularly an hydrosaline supplementation which gave him a daily intake of potassium of about 5 g. A stress test on a cycle ergometer showed many monomorphus premature ventricular beats which disappeared when the heart rate was higher than 110 beats/min. Moreover, 3629 polimorphus premature ventricular beats were recorded during a 24 hr ECG monitoring. At the time of the first examination, the plasma potassium concentration was 7,8 mEq x l(-1). The football player was then suspended from practicing sport and he was asked to stop his intake of potassium. The clinical examination was repeated after 3 and 6 months and no ventricular arrhythmias were observed during the stress test as well as during the 24 hours ECG monitoring. The plasma potassium concentration was normal again. The present case report is an example of how the misuse of saline supplementations could result in hyperkalemia and how this condition may lead to ventricular arrhythmias.     

Noninvasive monitoring of cardiac output during exercise by inductance cardiography

INTRODUCTION/PURPOSE: Inductance cardiography is a noninvasive technique that monitors changes in cardiac output from an inductance plethysmographic transducer encircling the chest at the level of the heart. The method has been previously validated in supine patients at rest by comparisons to thermodilution. Our purpose was to investigate whether the technique can be employed during bicycle exercise. METHODS: We simultaneously measured cardiac output by inductance cardiography and by two gas exchange methods based on the Fick principle during upright cycle ergometry in healthy volunteers. RESULTS: In 11 subjects, comparisons of changes in cardiac output by inductance cardiography agreed well with values measured by carbon dioxide rebreathing during a steady-state exercise protocol. In 12 subjects, cardiac output changes measured by inductance cardiography and an oxygen uptake method agreed closely during a progressive ramp exercise protocol to exhaustion. The bias (mean difference to reference methods) and limits of agreement (+/-2 SD of bias) for estimation of relative changes in cardiac output by inductance cardiography were 1% +/- 21% in 67 comparisons to the carbon dioxide rebreathing technique, and 0% +/- 22% in 98 comparisons to the oxygen uptake method. CONCLUSION: In healthy subjects, inductance cardiography accurately and unobtrusively estimates changes in cardiac output during bicycle exercise in comparison to gas exchange methods.     

Plasma and lymphocyte cyclic nucleotide response to acute exercise in healthy adults.

Plasma and lymphocytic cyclic nucleotide levels were assayed in 11 (5 male, 6 female) healthy normal adults before and after bicycle ergometry exercise. Lymphocytosis after exercise was observed. Plasma cAMP level was increased by almost 2 fold after exercise. However, plasma cGMP level was not affected. On the contrary, lymphocytic cAMP level was decreased by one third while cGMP level was halved. There were linear regression relationships between maximum heart rate and % difference in lymphocyte count and lymphocytic cyclic nucleotide levels pre- and post-exercise. Our findings demonstrate that higher cardiac output leads to increased lymphocytosis but decreased lymphocytic cyclic nucleotide levels.     

Heart rate responses during a breath-holding competition in well-trained divers

The diving response elicited by breath-holding (BH) and immersion mainly consists of bradycardia, decreased cardiac output, and peripheral vasoconstriction. These responses reduce oxygen consumption and thereby prolong the duration of the dive. They may also lead to cardiac arrhythmias or hypoxia, however, which in turn may play a role in the occurrence of syncope during BH. The aim of the present study was to analyze the cardiac responses to prolonged breath-holding in elite divers during a competition. Heart rate behaviour and the incidence of arrhythmia were recorded in 16 well-trained breath-hold divers (BHD) using a cardio-frequency meter (for 15 divers) and a Holter (for one diver) during maximal static breath-holding. Anthropometric, spirometric, and training characteristics such as percentage of body fat, pulmonary volumes and years of BH training were also determined. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV (1)) were higher than the predicted values (+7.7%, p<0.05 and+6.6%, p<0.05, respectively). During the static BH, divers presented apneic bradycardia (-44%) correlated with static BH times (p<0.05); this was associated with cardiac arrhythmias (supraventricular extrasystoles and ventricular extrasystoles) in the Holter-equipped subject. These results are in agreement with those obtained in laboratory conditions and confirm the existence of cardiac arrhythmias in well-trained BHD.     

Arrhythmias and conduction abnormalities in children after repair of tetralogy of Fallot

AIM: To find out types and frequency of cardiac arrhythmias and conduction abnormalities in the group of children who underwent surgery for tetralogy of Fallot (TOF). METHODS: Forty-six pedicatric patients who underwent a complete repair of TOF at the age of 1 to 13 (mean 2.89+/-2.36) were studied Thirty-eight (82.60%) had total correction and 8 (17.40%) had palliative operation first, and total correction afterwards. Twenty-four-hour Holter ECG monitoring was performed in all 46 pediatric patients aged from 1 to 16 yrs (mean 6.48+/-4.04) after surgery as follows: in 1 patient (2.17%) after a year, in 20 patients (43.477%) after 2 to 5 years and in 25 patients (54.34%) after 5 years. Mean age of patients on Holter monitoring was 9.25+/-4.39 (range 4-19). Twenty of them (43.47%) were girls and 28 (56.53%) were boys. All the patients were evaluated by standard methods (clinical signs, clinical findings, ECG before surgery, ECG before Holter monitoring and 2D Doppler echocardiography. RESULTS: Types of heart rhythm found out by Holter monitoring were: sinus nodus dysfunction in 1 child (2.17%), significant premature atrial contraction (PAC) in 8 (17.39%), supraventricular paroxysmal tachycardia in 3 (6.535), transient nodal rhythm in 2 (4.34%), premature ventricular contraction (PVC) Lown grade 1-III in 9 (19.56%) and Lown grade IV in 2 (4.34), atrioventricular (AV) block grade I in 2, right bundle branch block (RBBB) in all 46 (100%) and RBBB + left anterior hemiblock (LAH) in 4 (8.96%). There was no presence of atrial flutter, ventricular tachycardia or complete A V block. None of them experienced sudden death. Using cross procedure statistical methods, it was found that all the patients with PVC had right ventricular dilatation. There was no relation of other types of arrhythmia found on Holter monitoring to the other parameters from echocardiography, neither to the other standard methods. Children did not need the pace-maker, but 36.95% of the them required antiarrhythmic drugs. CONCLUSION: Twenty-four hour Holter ECG is a noninvasive and very sensitive method for discovering heart rhythm disturbances in children after the repair of tetralogy of Fallot, especially in asymptomatic patients. The patients after the repair of this congenital heart disease needed a long-term follow-up for early recognition of serious heart rhythm disturbances and their treatment.     

Predictive factors and mechanism of arrhythmias and myocardial ischaemic changes in elderly patients during barium enema.

The incidence of significant arrhythmias and ST segment changes during barium enema examination (BE) was evaluated by Holter monitoring of 58 unselected patients over the age of 60 years. Forty percent of the group developed new significant arrhythmias of which the most common were frequent and/or multifocal premature ventricular contractions. Seven percent demonstrated ST segment depression. Administration of glucagon did not diminish the incidence of arrhythmias. Predictive factors for ECG abnormalities were advancing age, abnormal pre-BE-ECG, and pre-BE orthostatic hypotension. Analysis of arhythmias and response to phywiologic tension. Analysis of arrhythmias and response to physiologic manoeuvres suggested that the abnormalities were related to increased sympathetic tone which may be intensified by hypovolaemia resulting from routine bowel preparation.     

Influence of arrhythmias on gated SPECT myocardial perfusion and function quantification.

Despite the importance of R-wave gating myocardial perfusion tomography for ventricular function assessment, neither prevalence of gating errors nor their influence on quantified cardiac parameters has been studied. METHODS: Arrhythmia-induced anomalies in curves of counts versus projection angle for each R-wave segment were detected visually and algorithmically. Arrhythmia prevalence was tabulated for 379 patients (group 1) with prospective coronary artery disease (mean age 63+/-13 y, 47% male). Myocardial counts were analyzed from all reconstructed cinematic midventricular slices to assess arrhythmia effects on percentage of systolic count increase, generally assumed to equal percentage of wall thickening. In a separate retrospective analysis of 41 patients (group 2), with coronary artery disease (mean age 64+/-12 y, 68% male) having no significant arrhythmias, 36 of whom also underwent equilibrium radionuclide angiography, original projection data were altered to simulate arrhythmia-induced aberrant count patterns to evaluate effects on ventricular function and perfusion measurements. RESULTS: Group 1 patients consisted of 26% without gating errors, 32% with count losses only in the last R-wave interval due to inconsistent transient increase of heart rate, 24% with count decreases in several late intervals due to consistently variable rates, 8% with early interval count increases paired with late interval count decreases due to ectopic beats and 9% with erratic count changes due to atrial fibrillation. Observed count patterns were strongly associated (P < 10(-3)) with arrhythmias detected by electrocardiogram monitoring. In group 2 simulations, ventricular volumes changed by only 2%+/-9% and ejection fraction (EF) by only 1%+/-4% from control values and correlated linearly (r> or = 0.96) with control values for all simulated arrhythmias. SPECT and equilibrium radionuclide angiography EFs correlated similarly (r = 0.85-0.89) for control and all simulations. Percentage changes from control in perfusion defect extent and severity were larger than processing reproducibility limits, the largest change being for atrial fibrillation. Control wall thickening was 38%+/-17%, significantly lower (P < 10(-6)) than for simulated arrhythmias, reflecting similar observations for group 1 patients. CONCLUSION: Even though ventricular volumes and EFs were affected minimally by arrhythmias, both perfusion analysis and wall thickening were compromised. Consequently, quality assurance of gating may be critically important for obtaining accurate quantified parameters.     

Military aviators with mitral valve prolapse: long-term follow-up and aeromedical endpoints

INTRODUCTION: Mitral valve prolapse (MVP) is a disqualifying condition for USAF aviators. Trained USAF aviators, and in recent years flying training applicants, may be granted waiver for initial or continued flying duties following extensive, periodic evaluation. This study examines the usefulness of the various tests performed in that evaluation process and provides long-term follow-up from 404 USAF flyers with MVP. METHODS: We retrospectively reviewed 2-dimensional echocardiography, Holter monitoring, treadmill exercise, thallium imaging, coronary fluoroscopy, cardiac catheterization, and centrifuge testing results from 404 military aviators evaluated at the Aeromedical Consultation Service between 1 January 1972 and 31 October 1993. Follow-up was achieved through questionnaires (91%) and death certificates, etc. RESULTS: Mean follow-up was 8.6 yr (range 1-21 yr). Age at study entry was 21 to 64 yr (mean = 36 yr). The occurrence rate for suddenly incapacitating events (sudden cardiac death, syncope, pre-syncope, and cerebral ischemic episodes) was 0.32%/yr. CONCLUSIONS: Echocardiographic MVP in military aviators is associated with a low but statistically increased prevalence of "incapacitating" aeromedical events. Univariate predictors of adverse outcome included study entry with an enlarged left ventricle or left atrium, cardiovascular symptoms or findings, or MVP with thickened leaflets. Evaluation of coronary artery disease (CAD) in this population, absent specific indicators of CAD risk, is not indicated.     

Heart Rate and PVCs During Exercise

In brief: Holter monitors were used to make ECG recordings on 48 men for six-hour periods on successive days—one day with and one without spontaneous exercise. The subjects were divided into four groups based on frequency of PVCs. There were no significant differences between the four groups' ages or heart rates during the control, exercise, and recovery periods. In subjects with PVCs there was a significant increase in the incidence of PVCs per hour and PVCs per 1,000 heart beats during exercise compared with the control period but no significant difference between exercise periods and the first hour of recovery. More complex arrhythmias occurred during exercise than during the control or recovery periods.     

Role of exercise stress test in master athletes

Background: The effectiveness of cardiovascular screening in minimising the risk of athletic field deaths in master athletes is not known. Objective: To evaluate the prevalence and clinical significance of ST segment depression during a stress test in asymptomatic apparently healthy elderly athletes. Methods: A total of 113 male subjects aged over 60 were studied (79 trained and 34 sedentary); 88 of them (62 trained and 26 sedentary) were followed up for four years (mean 2.16 years for athletes, 1.26 years for sedentary subjects), with a resting 12 lead electrocardiogram (ECG), symptom limited exercise ECG on a cycle ergometer, echocardiography, and 24 hour ECG Holter monitoring. Results: A significant ST segment depression at peak exercise was detected in one athlete at the first evaluation. A further case was seen during the follow up period in a previously "negative" athlete. Both were asymptomatic, and single photon emission tomography and/or stress echocardiography were negative for myocardial ischaemia. The athletes remained symptom-free during the period of the study. One athlete died during the follow up for coronary artery disease: he showed polymorphous ventricular tachycardia during both the exercise test and Holter monitoring, but no significant ST segment depression. Conclusions: The finding of false positive ST segment depression in elderly athletes, although still not fully understood, may be related to the physiological cardiac remodelling induced by regular training. Thus athletes with exercise induced ST segment depression, with no associated symptoms and/or complex ventricular arrhythmias, and no adverse findings at second level cardiological testing, should be considered free from coronary disease and safe to continue athletic training.