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1.
Comparison of the QT interval and corrected QT interval values that were calculated by the methods of Bazett (QTc1) and Fridericia (QTc2) were made between dogs with or without cardiac diseases to determine the influence of the QT interval on canine heart failure. Upon comparison of the measured values on ECG between the cardiac disease and non-cardiac disease groups, it was observed that the heart rate(HR) was significantly higher in the cardiac disease group than in the non-cardiac disease group, although the QT interval was similar in the two groups. The QTc1 and QTc2 were significantly longer in the cardiac disease group than in the non-cardiac disease group. With the progression of the New York Heart Association Class, the HR tended to increase. The QTc1 and QTc2 became significantly prolonged with the progression of heart failure. Nevertheless, because Bazett's correction formula is known to overcorrect when the HR is high, it was considered that the QTc1 was actually overcorrected by high HR with the progression of heart failure. The QTc2, on the other hand, was only slightly influenced by HR, suggesting that the prolongation was due to the progression of heart failure. These results suggest that the prolongation of QTc2 in cardiac disease reflects the substantial prolongation of the QT interval without the influence of HR. It is suggested that the QTc2 could be a useful parameter for assessing the degree of heart failure in dogs with cardiac disease.  相似文献   

2.
OBJECTIVE: To measure QT interval duration and QT dispersion in Boxers and to determine whether QT variables correlate with indices of disease severity in Boxers with familial ventricular arrhythmias, including the number of ventricular premature complexes per day, arrhythmia grade, and fractional shortening. ANIMALS: 25 Boxers were evaluated by ECG and echocardiography. PROCEDURE: The QT interval duration was measured from 12-lead ECG and corrected for heart rate (QTc), using Fridericia's formula. The QT and QTc were calculated for each lead, from which QT and QTc dispersion were determined. Echocardiography and 24-hour ambulatory ECG were performed to evaluate for familial ventricular arrhythmias. Total number of ventricular premature complexes, arrhythmia grade, and fractional shortening were determined and used as indices of disease severity. RESULTS: There was no correlation between any QT variable and total number of ventricular premature complexes, arrhythmia grade, or fractional shortening. No difference between QT dispersion and QTc dispersion was identified, and correction for heart rate did not affect the results. CONCLUSIONS AND CLINICAL RELEVANCE: QT interval duration and dispersion did not correlate with indices of disease severity for familial ventricular arrhythmias. Heart rate correction of the QT interval did not appear to be necessary for QT dispersion calculation in this group of dogs. QT dispersion does not appear to be a useful noninvasive diagnostic tool in the evaluation of familial ventricular arrhythmias of Boxers. Identification of affected individuals at risk for sudden death remains a challenge in the management of this disease.  相似文献   

3.
OBJECTIVE: To evaluate cardiac electrical function in the Spectacled Flying Fox (bat) infested with Ixodes holocyclus. DESIGN: Prospective clinical investigation of bats treated for naturally occurring tick toxicity. PROCEDURE: ECGs were performed on bats with tick toxicity (n = 33), bats that recovered slowly (n = 5) and normally (n = 5) following treatment for tick toxicity, and on normal bats with no history of tick toxicity (n = 9). RESULTS: Bats with tick toxicity had significantly prolonged corrected QT intervals, bradycardia and rhythm disturbances which included sinus bradydysrhythmia, atrial standstill, ventricular premature complexes, and idioventricular bradydysrhythmia. CONCLUSIONS: The QT prolongation observed on ECG traces of bats with tick toxicity reflected delayed ventricular repolarisation and predisposed to polymorphic ventricular tachycardia and sudden cardiac death in response to sympathetic stimulation. The inability to document ventricular tachycardia in bats shortly before death from tick toxicity may be explained by a lack of sympathetic responsiveness attributable to the unique parasympathetic innervation of the bat heart, or hypothermia-induced catecholamine receptor down-regulation. Bradycardia and rhythm disturbances may be attributable to hypothermia.  相似文献   

4.
Amiodarone, a class III antiarrhythmic with beta-adrenergic blocking and antimuscarinic properties, has a wide spectrum of clinical use in humans. This study was conducted to establish the effects of a 25 mg/kg q12h loading dose and a 30 mg/kg q24h maintenance dose of amiodarone, each given PO for 3.5 weeks, on systemic arterial pressure, echocardiographic (ECHO) indices of left ventricular function, ECGs, exercise tolerance, and serum biochemistries in adult, clinically normal dogs. Means were calculated and were compared by analysis of variance with repeated measures. When a significant F statistic was identified, specific means were compared by Bonferroni's post hoc test. Body weight and heart rate (HR) decreased, and PQ, QT, and corrected QT (QTc) increased significantly (P < .05) for the weeks that the dogs received the loading dose, but all parameters returned to values the same as those in the pretest for the weeks when dogs received the maintenance dose. Serum activity of hepatic enzyme activities and cholesterol concentrations increased, and serum concentrations of thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), phosphorous, and total carbon dioxide decreased. The changes in PQ, QT, and QTc are similar to those obtained previously, but the detailed ECG and ECHO observations have not been reported. A dose of 25 mg/kg q12h, but not 30 mg/kg q24h, is an appetite suppressant, and the lower dose produces neither ECG nor ECHO changes of clinical or toxicological significance in normal dogs.  相似文献   

5.
OBJECTIVE: To determine whether QT interval is prolonged or sudden death is caused by ventricular fibrillation resulting from torsades de pointes and to identify hemodynamic effects of ontazolast. ANIMALS: 28 Beagles. PROCEDURE: Physiologic variables were measured for 2 hours in conscious dogs given ontazolast (0, 1, or 3 mg/kg of body weight, IV) and for 1 hour in anesthetized dogs given cumulative doses of ontazolast (0, 1, 3, 6, or 8 mg/kg, IV). RESULTS: Ontazolast prolonged QT interval and QT interval corrected for heart rate (QTc) at doses of 6 mg/kg in anesthetized dogs. At 8 mg/kg, both variables remained prolonged but tended to decrease. In conscious dogs, ontazolast increased QT interval and QTc 15 minutes after administration, but both variables returned to reference ranges by 60 minutes. In conscious dogs, ontazolast increased maximum rate of increase of left ventricular pressure and maximal velocity of fiber shortening, indicators of inotropy, and increased tau, indicating a decreased rate of relaxation. One conscious dog receiving 3 mg/kg developed nonfatal torsades de pointes, but another conscious dog developed ventricular fibrillation. Two anesthetized dogs receiving 6 mg/kg developed early afterdepolarizations, and all dogs developed secondary components in theirT waves. CONCLUSION AND CLINICAL RELEVANCE: Ontazolast possesses potent class-III antiarrhythmic properties and induces prolongation of QTc in a dose-dependent fashion. Because there was a clear dose-dependent prolongation of QT interval in all instances, ontazolast may serve as a positive-control compound for studying other compounds that are believed to prolong the QT interval.  相似文献   

6.
观察氯仿对在体蟾蜍心电图的影响。用数字式心电图机记录蟾蜍用氯仿熏前、熏后即刻和恢复正常呼吸后的心电图的变化。结果表明,用氯仿熏后即刻或恢复正常呼吸后蟾蜍心电图与用氯仿前相比,心率减慢,QRS波群增宽,QT间期延长,T波明显,部分心电图出现大U波。氯仿不能导致蟾蜍发生室颤。  相似文献   

7.
Electrocardiographic (ECG) measurements were recorded in two subspecies of awake, apparently healthy, wild manatees (Trichechus manatus latirostris and T. m. manatus) undergoing routine field examinations in Florida and Belize. Six unsedated juveniles (dependent and independent calves) and 6 adults were restrained in ventral recumbency for ECG measurements. Six lead ECGs were recorded for all manatees and the following parameters were determined: heart rate and rhythm; P, QRS, and T wave morphology, amplitude, and duration; and mean electrical axis (MEA). Statistical differences using a t-test for equality of means were determined. No statistical difference was seen based on sex or subspecies of manatees in the above measured criteria. Statistical differences existed in heart rate (P = 0.047), P wave duration (P = 0.019), PR interval (P = 0.025), and MEA (P = 0.021) between adult manatees and calves. Our findings revealed normal sinus rhythms, no detectable arrhythmias, prolonged PR and QT intervals, prolonged P wave duration, and small R wave amplitude as compared with cetacea and other marine mammals. This paper documents the techniques for and baseline recordings of ECGs in juvenile and adult free-living manatees. It also demonstrates that continual assessment of cardiac electrical activity in the awake manatee can be completed and can be used to aid veterinarians and biologists in routine health assessment, during procedures, and in detecting the presence of cardiac disease or dysfunction.  相似文献   

8.
This study evaluated changes in electrocardiographic (ECG) parameters according to the stage of myxomatous mitral valve disease (MMVD) in dogs, as well as the utility of ECG parameters as prognostic indicators for congestive heart failure (CHF). Medical records of dogs with MMVD were retrospectively searched. Dogs with MMVD (N = 101) were classified into stages B [B1 (n = 52) and B2 (n = 23)] and C (n = 26) according to the American College of Veterinary Internal Medicine guidelines. Baseline variables were collected; these included signalment, radiographic, echocardiographic, and ECG parameters. Corrected QT intervals (QTc) were calculated using the logarithmic (QTc1) and Fridericia (QTc2) formulas. The P wave duration, QTc1, and QTc2 were significantly longer in stage C than in stage B. The P wave duration cutoff of 43.5 ms had a diagnostic accuracy of 65% for differentiating CHF, with a sensitivity of 63% and a specificity of 90%. A cutoff value of 307.8 ms for QTc1 yielded a sensitivity of 62%, a specificity of 76%, and a diagnostic accuracy of 78%, and a cutoff value of 239.2 ms for QTc2 yielded a sensitivity of 62%, a specificity of 83%, and a diagnostic accuracy of 77% for diagnosing CHF. Therefore, prolonged P wave and QTc in dogs with MMVD may facilitate the prediction of CHF. Electrocardiography could provide clinicians with a readily available and cost-effective screening tool for predicting CHF, if the usefulness of ECG parameters can be verified.  相似文献   

9.
Moxifloxacin has been shown to induce QT prolongation in both clinical and preclinical models. However, the ability to observe this effect at clinically relevant concentration in normal conscious dogs has not been reported. The purpose of this study was to investigate the effects of moxifloxacin on the QT interval in conscious, healthy dogs. Four male mongrel dogs were chronically instrumented for the measurement of arterial blood pressure, left ventricular blood pressure, cardiac output, electrocardiograms (ECGs), and body temperature. Animals were administered a 1-h i.v. infusion of moxifloxacin once per day via a catheter in the cephalic vein. Each dog received all doses (0, 1, 10, 25 and 50 mg/kg) in an escalating fashion. Moxifloxacin caused a statistically significant increase in arterial blood pressure at 50 mg/kg. A dose-response effect on QT and QTc prolongation was observed. A statistically significant prolongation in the QT interval was observed at 10, 25 and 50 mg/kg and a prolongation of QTc was observed at 25 and 50 mg/kg. These effects occurred at clinically relevant plasma concentrations. This study demonstrate that a study design with four dogs was sensitive enough to measure moxifloxacin-induced QT prolongation at clinically relevant plasma concentrations.  相似文献   

10.
Disorders of the thyroid gland activity are the most commonly encountered disturbances of endocrine origin in the dog. Hypo- or hyperthyroidism may disturb the function of the cardiovascular system and cause arrhythmias. The aim of this study was to evaluate the influence of thyroid gland activity on electrocardiogram (ECG) picture in the dog by comparing ECG curves of healthy dogs, dogs with hypothyroidism and dogs with cardiac insufficiency caused by endocardiosis of the mitral valve. The study was performed on 38 dogs, patients of the Department of Internal and Parasitic Diseases with Clinic for Horses, Dogs and Cats in Wroc?aw. The animals were assigned to 3 groups: Group I--control group, 13 clinically healthy dogs; Group II--14 dogs with diagnosed cardiac insufficiency caused by endocardiosis of the mitral valve; Group III--11 dogs with hypothyroidism. Clinical examination of the animals was conducted according to the following pattern: anamnesis, general clinical examination, cardiological examination (ECG, USG of the heart) and laboratory analysis (triacylglycerydes, cholesterol, T3, T4, FT4). In this study, the significant influence of thyroid gland activity on ECG picture of the evaluated dogs was found. In the dogs with hypothyroidism a decrease in the sino-atrial node activity was observed, which led to decreased heart rate. In dogs with hypothyroidism, the innerheart conduction was reduced, which was demonstrated by prolongation of the P wave, QRS complex and the QT interval.  相似文献   

11.
The purpose of this study was to evaluate the electrocardiographic effects of single intravenous dose of ciprofloxacin in dogs. Ten adult cross-breed dogs of both sexes were selected as the sample population. Baseline electrocardiographic values were recorded just before drug administration. Then the dogs received intravenous infusion of ciprofloxacin (10 mg/kg) over the fifteen minutes. The ECGs recorded at 15, 30, 60 and 120 minutes after ciprofloxacin administration. The ECG measurements of heart rate, PR interval, QRS interval, ST segment, T-wave amplitude and QT interval were taken from lead II. There was a small but significant increase in the longest QT intervals over baseline at T60 (P = 0.041). The mean PR intervals, QTc intervals, JT intervals, ST segment, T-wave amplitude did not differ significantly before and after ciprofloxacin except for JT intervals at T60 (P = 0.041). At this measurement point, there was an increased QT interval value of 0.02 second or 9.51 % in comparison to the baseline. In Conclusions, Only minor QT intervals changes were observed after ciprofloxacin injection. Despite the occurrence of ECG changes following intravenous ciprofloxacin administration neither dangerous rhythm disturbances nor serious ECG changes were seen in this study.  相似文献   

12.
The experiment studied the effects of oral Echinacea purpurea on heart rate, ECG, blood pressure and respiration of awake Beagle dogs. Experimental results showed that oral Echinacea purpurea 0.125 to 1.25 g/kg could apparently reduced the heart rate of awake Beagle dogs, and had no significant effects on blood pressure, respiration and ECG between P wave, T wave, R wave, QT interval, PR interval as well as QRS duration （P>0.05）. It showed that Echinacea purpurea had no apparent effects on the dog’s respiratory system and cardiovascular system, which was safe and reliable in application doses.  相似文献   

13.
OBJECTIVE: To develop a clinically useful model for predicting QT interval duration as a function of heart rate in healthy cats. ANIMALS: 20 healthy cats. PROCEDURE: For all cats, results of a physical examination, electrocardiography, and echocardiography were normal. Twenty-four hour heart rate and rhythm data were collected by means of ambulatory electrocardiography. Hourly ECG segments were obtained from the 24-hour recordings. Mean heart rate and the mean of 5 QT interval measurements were calculated for each of 479 usable ECG segments. Analysis of covariance was used to develop models to describe variability in QT interval duration. RESULTS: Prediction equations (R2 = 0.81) including terms for heart rate, (heart rate)2, age group (1 to 4 vs 8 to 14 years old), and their interactions were developed. Sex, individual cat, and time of day were of little value in predicting QT interval duration. A simplified prediction equation without age group (R2 = 0.71) also was developed and had better predictive ability than reported correction formulas for QT interval duration. CONCLUSIONS AND CLINICAL RELEVANCE: Prediction equations with 95% prediction intervals for expected QT interval duration in healthy cats were generated. Abnormal QT interval duration can be associated with cardiac electrical instability, yet QT interval duration is greatly influenced by heart rate. Results of the present study provide reference ranges for expected QT interval duration as a function of heart rate in healthy cats.  相似文献   

14.
OBJECTIVES: To determine effects of tricyclic antidepressants (TCA) on the ECG of dogs treated for behavioral conditions and to examine correlations between ECG findings and serum concentrations of these medications. DESIGN: Repeated-measures study. ANIMALS: 39 client-owned dogs with behavioral problems. PROCEDURE: Two groups of dogs with behavioral problems were evaluated. In group 1 (n = 20), ECG tracings were recorded before starting treatment with TCA and again after treatment for > or = 1 month. Dogs in group 2 were already on long-term maintenance amounts of antianxiety medication when ECG tracings were recorded and serum concentrations of medications were obtained. RESULTS: Significant differences were not detected for dogs in group 1 between ECG values measured before and after TCA administration. The ECG values for dogs in group 2 did not differ significantly from the mean of group-1 dogs before receiving medication or from the reference range used at our facility. Duration of the P wave had a significant positive correlation with serum concentrations of clomipramine but significant negative correlation with serum concentrations of amitriptyline. The QT interval corrected for heart rate had a significant negative correlation with serum concentrations of amitriptyline. CONCLUSIONS AND CLINICAL RELEVANCE: Amitriptyline and clomipramine administered at standard dosages apparently do not cause ECG abnormalities in healthy dogs with behavioral problems. These medications should be used cautiously in dogs with conduction abnormalities, and clinicians should periodically monitor ECG and use good clinical judgment to weigh risks and benefits of medications for the safety of each dog.  相似文献   

15.
张谊 《中国畜牧兽医》2014,41(8):149-154
为探讨Ca2+、K+对犬心功能的影响及其在治疗犬电解质紊乱疾病中的作用,选取24～48月龄中华田园犬20只,公母各半,按年龄、性别及体重均分成2组。Ⅰ组按照1.5 mL/min对试验犬静脉注射5% KCl建立高钾血症模型,然后按照1 mL/min对其静脉注射适量CaCl2以缓解其临床症状;Ⅱ组按照1 mL/min对试验犬静脉注射5% CaCl2建立高钙血症模型,然后按照1.5 mL/min对其静脉注射适量KCl缓解其临床症状。采集试验犬在模型建立前、后及对模型犬注射CaCl2（KCl）后血液2 mL,分离血清检测血清中K+、Ca2+、Na+、Cl-离子浓度,同时监测各采样点试验犬血压、心率和心电图变化。结果显示,试验犬按照1.5 mL/min静脉注射5% KCl可成功建立高钾血症模型,此时血清K+浓度显著升高（P＜0.05）,心率极显著下降（P＜0.01）,收缩压显著下降（P＜0.05）,心电图表现为心脏节律不齐,P波低平甚至消失,T波高尖呈斗篷状;对高钾血症模型犬静脉注射CaCl2后,血清K+浓度显著下降（P＜0.05）,心率显著升高（P＜0.05）,心电图中P波重新出现,斗篷状的T波消失。按照1 mL/min静脉注射5% CaCl2可成功建立高钙血症模型,此时血清Ca2+浓度极显著升高（P＜0.01）,Na+浓度显著下降（P＜0.05）,心率显著升高（P＜0.05）,脉压极显著下降（P＜0.01）,心电图表现为S-T段缩短甚至消失、T波增宽、Q-T间期缩短、出现特征性U波等变化;对高钙血症模型犬注射KCl后血清Ca2+浓度下降但差异不显著（P＞0.05）,心率显著下降（P＜0.05）,基本恢复正常,脉压持续下降但差异不显著（P＞0.05）,此时心电图中T波明显升高、S-T段时限有所增加、U波消失等变化。结果表明静脉注射5% KCl（5% CaCl2）可成功建立犬高钾血症（高钙血症）模型。对高钾血症犬静脉注射CaCl2可使其心功能显著恢复;而对高钙血症犬静脉注射KCl其心功能恢复欠佳。  相似文献   

16.
OBJECTIVE: To determine whether serum concentrations of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) are increased in dogs with gastric dilatationvolvulus (GDV) and whether concentrations correlate with severity of ECG abnormalities or outcome. DESIGN: Prospective case series. ANIMALS: 85 dogs with GDV. PROCEDURE: Serum cTnl and cTnT concentrations were measured 12 to 24, 48, 72, and 96 hours after surgery. Dogs were grouped on the basis of severity of ECG abnormalities and outcome. RESULTS: cTnl and cTnT were detected in serum from 74 (87%) and 43 (51%) dogs, respectively. Concentrations were significantly different among groups when dogs were grouped on the basis of severity of ECG abnormalities (none or mild vs moderate vs severe). Dogs that died (n = 16) had significantly higher serum cTnI (24.9 ng/ml) and cTnT (0.18 ng/ml) concentrations than did dogs that survived (2.05 and < 0.01 ng/ml, respectively). Myocardial cell injury was confirmed at necropsy in 4 dogs with high serum cardiac troponin concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that concentrations of cTnI and cTnT suggestive of myocardial cell injury can commonly be found in serum from dogs with GDV and that serum cardiac troponin concentrations are associated with severity of ECG abnormalities and outcome.  相似文献   

17.
Serial electrocardiograms were recorded from 70 Mastín Español dogs in right lateral recumbency, aged between one day and three years, in order to observe the changes in the waveform and intervals, QRS morphology, cardiac rhythm and heart rate caused by their growth. Age and bodyweight caused a gradual increase in the duration and amplitude of the P wave, duration of the PR, QT and RR intervals, amplitude of the R wave and duration of the QRS complex and ST segment. Q wave was observed in nearly all the recordings with different amplitudes. The S wave was only significant in one-day-old animals and QRS morphology showed significant important changes from qrS and rS to qR and qRs morphologies during the first two weeks of life. The T wave increased its amplitude until the age of two months and changed its polarity (from negative to positive) from five months of age onwards. The heart rate decreased until the age of seven months, reaching stabilised values of 110 ± 7-3 beats per minute. Sinus tachycardia was commonplace in animals under one month old and respiratory sinus arrhythmia was found from six months of age. Sex only influenced the duration and amplitude of the T wave. Males had higher mean values than females.  相似文献   

18.
The main purpose of this study was to describe electrocardiographic (ECG) changes in canine babesiosis, and to relate these to clinical severity, outcome and cardiac pathology.Four groups of dogs with babesiosis were studied: mild to moderate anemia, severe anemia, concurrent autoagglutination and concurrent complications. Lead II ECG was recorded at admission for 1 minute in all dogs (121). A six lead ECG was recorded in 88 dogs. Full necropsy was performed on 16 dogs (5 died on arrival, 11 had ECG recording).The following ECG changes were recorded in relatively high prevalence: sinoatrial blocks or sinus arrest (7%), ventricular premature complexes (7%), low R-amplitude (23%), prominent Q (13%), axis deviations (40%), prolonged QRS (32%), ST depression and coving (28%), large T (42%), and notched R (28%). Differences between groups were minor. There was a significantly higher prevalence of sinus bradycardia and irregular rhythm in the non-survivors. Gross pathological changes were pericardial effusion and hemorrhages. Histological changes were hemorrhages, necrosis, inflammation and fibrin microthrombi. The only correlation between pathology and ECG was low R-amplitude and pericardial effusion.The ECG changes were similar to the pattern described for myocarditis and myocardial ischemia, and together with the histopathological findings indicated that the heart suffers from the same pathological processes described in other organs in canine babesiosis, namely inflammation and hypoxia. As the clinical application of the ECG changes found in this study was limited, cardiovascular assessment should be based on functional monitoring rather than ECG.  相似文献   

19.
OBJECTIVE: To compare 6-lead ECG traces in clinically normal conscious dogs in a sitting position and sternal recumbency to that of right lateral recumbency. ANIMALS: 31 healthy dogs with no history of cardiac disease. PROCEDURE: Six-lead ECGs were recorded for dogs in right lateral recumbency, a sitting position, and sternal recumbency. Q-, R-, and S-wave amplitudes as well as QRS-complex duration were measured in all leads. Additionally, P-wave amplitude and duration, PR interval, ST-segment elevation or depression, and OT interval were measured in lead II. RESULTS: Compared with measurements in right lateral recumbency, the sitting position resulted in increased Q-wave amplitude (lead III), increased R-wave amplitude (leads I and aVL), decreased R-wave amplitude (leads III and aVF), increased S-wave amplitude (lead aVR), decreased S-wave amplitude (lead aVL), increased P-wave amplitude (lead II), and a leftward shift in the mean electrical axis. Compared with measurements in right lateral recumbency, sternal recumbency resulted in decreased Q-wave amplitude (leads I, II, and aVF), increased R-wave amplitude (leads 11, III, and aVF), decreased R-wave amplitude (lead aVR), increased S-wave amplitude (lead aVR), increased P-wave amplitude (lead II), and decreased ST-segment depression (lead II). Compared with right lateral recumbency, the sitting position or sternal recumbency did not result in significant differences in PR interval, QT interval, or QRS-complex duration. CONCLUSIONS AND CLINICAL RELEVANCE: Significant changes are found in ECG measurements in the sitting position and sternal recumbency, compared with right lateral recumbency. In dogs, many ECG reference range values for right lateral recumbency are not valid for ECGs obtained in the sitting position or sternal recumbency.  相似文献   

20.
OBJECTIVE: To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval. ANIMALS: 100 sled dogs in Alaska. PROCEDURE: Dogs were examined in early September (before training) and late March (after training). During the interim, dogs trained by pulling a sled with a musher (mean, 20 km/d). Standard and signal-averaged ECG were obtained before and after training. RESULTS: Endurance training significantly increased mean QRS duration by 4.4 milliseconds for standard ECG (mean +/- SEM; 62.3 +/- 0.7 to 66.7 +/- 0.6 milliseconds) and 4.3 milliseconds for signal-averaged ECG (51.5 +/- 0.7 to 55.8 +/- 0.6 milliseconds) without changing body weight. Increase in QRS duration corresponded to a calculated increase in heart weight (standard ECG, 23%; signal-averaged ECG, 27%). Signal-averaged QRS duration was correlated with echocardiographically determined left ventricular diastolic diameter for the X orthogonal lead (r = +0.41), Y orthogonal lead (r = +0.33), and vector (r = +0.35). Training also increased QT interval (234 +/- 2 to 249 +/- 2 milliseconds) and R-wave amplitude in leads II and rV2, increased peak-to-peak voltage and S-wave amplitude in the Y orthogonal lead, and decreased Q-wave amplitude in the Y orthogonal lead. CONCLUSIONS AND CLINICAL RELEVANCE: Electrocardiographic changes reflected physiologic cardiac hypertrophy in these canine athletes in response to repetitive endurance exercise. The QRS duration increases in response to endurance exercise training and, therefore, may be of use in predicting performance in endurance activities.  相似文献   

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