The giant R wave of acute myocardial infarction

The common clinical electrocardiographic criteria for diagnosis of acute transmural myocardial infarction include ST segment elevation and tall, upright T waves, but do not include changes in QRS morphology. The purpose of this study was to show that development of a 50% or greater increase in R wave amplitude, the giant R wave, in patients with acute transmural myocardial infarction occurs, and also to characterize changes in QRS morphology which may aid the ECG diagnosis of acute transmural myocardial infarction. Over the past 6 years, 36 patients with an increase in R wave amplitude during acute transmural myocardial infarction were identified at the Strong Memorial Hospital Coronary Care Unit. A significant increase in R wave height (0.33 +/- 0.10 to 0.97 +/- 0.08 mV, p less than 0.05), width (0.03 +/- 0.00 to 0.08 +/- 0.01, p less than 0.05) and area (0.01 +/- 0.00 to 0.05 +/- 0.01 mV-msec, p less than 0.05) appeared in the same ECG lead demonstrating ST segment elevation and tall T waves during the acute phase of transmural myocardial infarction. Patients with diaphragmatic myocardial infarction showed a significant (p less than 0.05) rightward QRS frontal plane axis shift and patients with anterior wall myocardial infarctions developed an anterior QRS axis shift in the horizontal plane during occurrence of the giant R wave. We conclude from this preliminary study that the giant R wave may be observed during acute transmural myocardial infarction and may in part be caused by local intramyocardial conduction delay in acutely ischemic tissue as supported by an increase in the R wave width along with shifts in the frontal and horizontal plane QRS axis toward the area of acute ischemia. The giant R wave occurs in conjunction with ST segment elevation and tall T waves and may aid the ECG diagnosis of acute transmural myocardial infarction.     

Normalization of abnormal T waves in ischemia.

Inverted T waves due to coronary artery disease and previous myocardial infarction were observed to revert ot normal, upright position during ischemia in 38 patients. The normalization of inverted T waves was seen on the electroencephalograms of 19 patients during spontaneously occurring angina pectoris and of 11 patients when ischemia was provoked by treadmill exercise; for 8 patients, normalization occurred during the administration of isoproterenol hydrochloride and during the consequent episode of angina pectoris. The mechanism for normalization may be the algebraic sum of the extent of ST segment elevation and the amplitude of the T waves of acute ischemia plus the extent of preexisting ST segment depression and the degree of T wave inversion, to result in isoelectric ST segment and upright T wave. As with myocardial infarction, reciprocal changes may also be recorded. However, the reciprocal nature may be masked since either acute ST segment elevation of T wave inversion, or both, may not be recorded in the leads reflecting the ischemic area because of normalization.     

Class I antiarrhythmic drug and coronary vasospasm-induced T wave alternans and ventricular tachyarrhythmia in a patient with Brugada syndrome and vasospastic angina

A 50-year-old man presented with a history of transient chest pain and palpitations. The 12-lead ECG at rest showed normal sinus rhythm. A slight ST segment elevation was observed in leads V1 to V3. During hospitalization, atrial fibrillation developed, and oral pilsicainide was administered. Thirty minutes after the drug was given, the ECG showed marked ST segment elevation in leads V1 to V3, and T wave alternans became visible in leads V2 and V3. Self-terminating ventricular tachycardia was initiated following frequent ventricular premature complexes, which showed a left bundle branch block pattern. The coronary angiogram was normal, but in the provocation test of vasospastic angina, acetylcholine administration into the left coronary artery resulted in complete occlusion of the left anterior descending and circumflex arteries. Marked ST segment elevation developed in leads I, aVL, and V3 to V6 concomitant with visible QT/T alternans in leads V4 and V5, and ventricular tachyarrhythmia was initiated. Brugada syndrome and vasospastic angina coexisted in this patient, and T wave alternans can be used as a predictor of ventricular tachyarrhythmias in such patients.     

平板运动试验诱发ST段抬高对冠状动脉病变部位定位诊断的意义

目的探讨平板运动试验诱发ST段抬高对冠心病的诊断价值及对冠状动脉病变部位定位诊断的意义。方法分析8例无心肌梗死而运动诱发ST段抬高的运动心电图及冠状动脉造影检查结果。结果8例患者冠脉造影均显示有程度不等的血管狭窄(50%￣100%);ST段抬高导联与缺血相关血管有良好对应关系。结论无心梗患者运动诱发心电图ST段抬高是冠脉痉挛或冠脉严重狭窄所致心肌局部缺血的标志,且对预测冠状动脉病变部位有一定意义。     

Changes in the electrocardiographic response to exercise in healthy women

Changes in the P wave, QRS complex, ST segment, and T wave during and after maximal exercise were quantitatively analysed in 116 healthy women with a mean age of 39. The corrected orthogonal Frank lead electrocardiogram was continuously recorded and computer processed during bicycle ergometry. With exercise, maximal spatial P wave vectors shifted downward. The Q wave amplitude became more negative and the R wave amplitude diminished considerably in leads X and Y: the S wave amplitude decreased only slightly in these leads. The QRS vectors shifted towards right and posteriorly during exertion and a further shift in the same direction was seen in the recovery period. The ST segment amplitude 60 ms after the J point decreased with exertion and became negative at heart rates above 140 beats per minute, in particular in lead Y. ST segment depression increased with age. The T wave amplitude decreased during exercise and increased sharply in the recovery period. Though mean R wave amplitude in leads X and Y became more negative with exercise, this response was unpredictable in individual women. The exercise induced changes in QRS vectors in women resembled those described in men. Changes in the amplitude of the R wave should not be used for the diagnosis of coronary disease in women. ST segment depression was more pronounced in the inferiorly oriented lead Y than in lead X but it was unrelated to changes in the QRS vectors in these leads.     

Changes in the electrocardiographic response to exercise in healthy women.

Changes in the P wave, QRS complex, ST segment, and T wave during and after maximal exercise were quantitatively analysed in 116 healthy women with a mean age of 39. The corrected orthogonal Frank lead electrocardiogram was continuously recorded and computer processed during bicycle ergometry. With exercise, maximal spatial P wave vectors shifted downward. The Q wave amplitude became more negative and the R wave amplitude diminished considerably in leads X and Y: the S wave amplitude decreased only slightly in these leads. The QRS vectors shifted towards right and posteriorly during exertion and a further shift in the same direction was seen in the recovery period. The ST segment amplitude 60 ms after the J point decreased with exertion and became negative at heart rates above 140 beats per minute, in particular in lead Y. ST segment depression increased with age. The T wave amplitude decreased during exercise and increased sharply in the recovery period. Though mean R wave amplitude in leads X and Y became more negative with exercise, this response was unpredictable in individual women. The exercise induced changes in QRS vectors in women resembled those described in men. Changes in the amplitude of the R wave should not be used for the diagnosis of coronary disease in women. ST segment depression was more pronounced in the inferiorly oriented lead Y than in lead X but it was unrelated to changes in the QRS vectors in these leads.     

Long-term evaluation of early repolarization syndrome (normal variant RS-T segment elevation).

The electrocardiograms of 65 patients with the "early repolarization syndrome" (normal variant of RS-T elevation) were analyzed to delineate the features and evaluate the natural history of this electrocardiographic entity. Maximal follow-up was 26 years. The syndrome was characterized by (1) an upward concave elevation of the RS-T segment with distinct or "embryonic" J waves, slurred downstroke of R waves or distinct J points or both; (2) RS-T segment elevation commonly encountered in the precordial leads and more distinct in these leads; (3) rapid QRS transition in the precordial leads with counterclockwise rotation; and (4) persistence of these characteristics for many years although some intraindividual changes were common. Less commonly found were (5) tall R and T waves in the precordial leads; (6) "labile" or "juvenile" T wave patterns; (7) "pseudo-R" waves; and (8) "isolated T negativity syndrome." These changes commonly simulate pericarditis, myocardial ischemia, left ventricular hypertrophy and right bundle branch block.     

急性前壁心肌梗死R波、Q波和ST段演变速度的观察

目的 通过心电图对急性心肌梗死的诊断提供更多的信息。方法 对21例急性前壁心肌梗死患者进行R波、Q波和ST段变化进行同步12导联心电图动态观察。将开始到结束的7次标测分成6个时间间隔．分别计算各个时间间隔的∑R、∑Q、和∑ST的平均值和标准差。结果∑R于胸痛发作后12h内迅速下降；∑Q逐渐增大，24h内变化最显著；EST 12h内迅速下降，48h后渐趋稳定。12例（57％）R波消失，Q波在发病后12h内形成；另9例（43％）于24h内形成。结论心肌梗死后ST段抬高、R波下降和Q波形成在快速型和慢速型心肌梗死患者中不同。     

Origin of the giant R wave in acute transmural myocardial infarction in the pig

An increase in R wave amplitude and a diminution of S wave amplitude, together with ST segment elevation, have been described as very early electrocardiographic changes during clinical and experimental acute myocardial infarction. The genesis of these QRS changes remains unclear. We assessed the quantitative relationship between the local conduction delay and the formation of the giant R wave, using multiple epicardial, intramural unipolar, and bipolar electrodes in 30 open-chest pigs with acute transmural myocardial ischemia. Blood pressure, heart rate, serum electrolytes, hematocrit, and left ventricular size remained constant, or varied insignificantly throughout the experiments. In nonischemic pigs, transmural left ventricular activation occurred nearly simultaneously, and the activation time was not correlated with the net QRS potential. During acute ischemia, a giant R wave developed at all of the electrodes located within the ischemia region; R wave amplitude began to increase 1 min after coronary artery ligation (p less than 0.05), compared to control amplitude and peaked at 8 min (p less than 0.0001). The degree of conduction delay at a given site was correlated linearly with the local R wave amplitude (average of correlation coefficients +/- SEM at 1 min, r = 0.64 +/- 0.08, and at 8 min, r = 0.81 +/- 0.06). The magnitude of the R wave potential and the conduction delay were greater in regions deep inside the ischemic zone than in the border and normal areas (p less than 0.0001), and were greater in subepicardial than in subendocardial areas (p less than 0.05). In summary, during transmural ischemia, conduction is markedly slowed, and an orderly and discrete wavefront advances toward the center of the ischemic zone from lateral and subendocardial areas. When depolarization is complete in the rest of the heart, this slow activation front becomes temporally isolated and its progression gives rise to a giant R wave, which appears in recordings from overlying electrodes.     

活动平板运动试验诱发ST段抬高的临床意义

为探讨活动平板运动试验诱发ST段抬高的临床意义 ,分析了 9例无心肌梗死 (简称心梗 )而运动诱发ST段抬高的静息心电图、运动试验及冠状动脉 (简称冠脉 )造影检查结果。结果 :5 0 5 5例行平板运动试验者中 ,有 11例未患心肌梗死而运动诱发心绞痛伴ST段抬高 ,发生率 0 .2 2 %。其中 ,8例患者作了进一步检查 ,冠脉造影显示均有程度不等的血管病变 ,缺血相关血管的狭窄达到 5 0 %～ 10 0 %。ST段抬高导联与缺血相关血管有良好对应关系。另有 1例患者于运动试验 1周后死于心脏性猝死。结论 :无心梗患者运动诱发心电图ST段抬高是冠脉痉挛或冠脉严重狭窄所致心肌局部缺血的标志。     

Electrocardiographic differentiation between right coronary and left circumflex coronary arterial occlusion in isolated inferior wall myocardial infarction

The presence of atrioventricular block and ST segment elevation in lead V4R accurately predicts right coronary artery occlusion in patients with inferior wall myocardial infarction. However, these electrocardiographic signs are absent in the majority of patients with inferior myocardial infarction. We studied ST segment elevation in leads II and III, ST segment in lead I and T wave polarity in lead V4R in order to differentiate between right coronary artery and left circumflex coronary artery occlusions in 104 patients with inferior myocardial infarction who subsequently underwent coronary angiography. The ST segment elevation was greater in lead III than in lead II when the right coronary artery was the culprit vessel and vice versa when the left circumflex was the culprit vessel (p < 0.001). An upright T wave in lead V4R and ST segment depression in lead I was common when the right coronary artery was the culprit vessel and not seen with left circumflex occlusion (p < 0.001). ST segment elevation in lead III was higher than in lead II with a sensitivity of 99 percent and a specificity of 100 percent for diagnosing right coronary artery as the culprit vessel. ST segment elevation in lead II was higher than in lead III with a sensitivity of 93 percent and a specificity of 100 percent in identifying the left circumflex as the culprit vessel. Thus, these signs are very useful in identifying the culprit vessel in inferior myocardial infarction.     

Variant Brugada syndrome--mild ST segment elevation in inferior leads and aborted sudden cardiac death

We describe a case of an otherwise healthy 48-year-old man who survived aborted sudden cardiac death (SCD). His ECG showed ST segment elevation in inferior leads, therefore an acute coronary syndrome was suspected. However, serial troponin T and CPK-MB were negative, echocardiogram was unremarkable and exercise test was negative. On the basis of electrophysiological study, positive ajmaline test, persistent ST segment elevation in inferior leads and other clinical features (PQ interval of 240 ms, family history of SCD) a diagnosis of variant Brugada syndrome was made. Persistent ST segment elevations in inferior leads can be a marker of variant Brugada syndrome.     

The Initial Electrocardiographic Pattern in Acute Myocardial Infarction

Background: The ECG is the most widely used accessory for early diagnosis and risk stratification of patients with acute myocardial infarction (AMI). Previous studies have concentrated on the association between either the number of leads with ST segment deviation (elevation and depression) or the total amount of ST segment elevation and/or depression and prognosis. However, the results are conflicting. Methods: A different method is to use the grades of ischemia as an estimate of infarct or size and prognosis. Grade I ischemia is defined as tall peak T waves with < 0.1 mV ST segment elevation; grade II as ST segment elevation with positive T waves, without distortion of the terminal portion of the QRS; and grade III as ST segment elevation, positive T waves, and distortion of the terminal portion of the QRS. Grade III ischemia on the admission ECG is associated with larger final infarct size and increased mortality. Results: In patients with inferior wall AMI, especially those with prior infarction, the pattern of precordial ST segment depression is even more important and maximal ST depression in V4-V6 is associated with high mortality. Moreover, meticulous interpretation of the initial ECG pattern provides information about the probable site of the culprit obstructive coronary lesion. Conclusion: Thus, the admission ECG of AMI can assist not only in diagnosis, but also in estimation of infarct size, correlation with the underlying coronary anatomy and risk stratification.     

心电图对非ST段抬高型急性冠脉综合征危险分层的价值

目的探讨心电图变化对非ST段抬高型急性冠状动脉综合征患者危险分层的价值。方法自2006年1月-2007年7月，在我院因急性胸痛拟诊不稳定型心绞痛及非ST段抬高心肌梗死而收入住院且记录资料完整的616例患者。人院后采集病史、查体，并在10min内完成常规18导联心电图检查，将患者人院时心电图的改变分为ST段压低组（包括伴有T波倒置者）、单纯T波倒置组、尚不能诊断的心电图组及正常心电图组；又将ST段压低组分为：胸前导联（V4-V6）ST段压低合并负向T波、胸前导联ST段压低合并正向T波、其他导联ST段压低合并正向T波、其他导联ST段压低合并负向T波4组。观察各组住院期主要心血管事件（心脏性死亡、非致命性心肌梗死、反复缺血性心绞痛发作），并随访1-12（7．2±3．8）个月，观察主要心血管事件变化。结果与正常心电图组比较；ST段压低组的复合心血管事件明显增多。胸前导联ST段压低合并T波倒置组的患者较其他导联ST段压低合并或不合并T波倒置组的复合心血管事件明显增多。结论．心电图的ST段变化对非ST段抬高型急性冠状动脉综合征患者的危险分层及心血管事件预测均有重要价值。     

Intravenous administration of class I antiarrhythmic drugs induced T wave alternans in a patient with Brugada syndrome

A 71-year-old man who experienced aborted sudden death was referred to our hospital. Coronary artery disease and cerebral accident were ruled out by conventional tests. The 12-lead ECG obtained at rest showed a right bundle branch block pattern and ST segment elevation in leads V1 to V3. Double ventricular extrastimuli at coupling intervals >180 msec induced ventricular fibrillation (VF) twice during electrophysiologic study. Intravenous administration of procainamide accentuated ST segment elevation in leads V1 to V3, and visible T wave alternans was induced in leads V2 and V3 at a dose of 450 mg. Initiation of T wave alternans was not associated with changes of the cardiac cycle or development of premature beats. When procainamide infusion was discontinued, T wave alternans disappeared before the elevated ST segment returned to the control level. Pilsicainide also accentuated ST segment elevation and induced similar T wave alternans in leads V2 and V3. Class I antiarrhythmic drug-related T wave alternans has been reported rarely in Brugada syndrome, but it may represent enhanced arrhythmogenicity of VF. We need to monitor closely and study the clinical implications of T wave alternans in Brugada syndrome.     

U wave inversion during attacks of variant angina.

Sequential 12 lead electrocardiograms were recorded during angina pectoris induced by ergonovine maleate in 38 patients with variant angina. Transient U wave inversion was observed in 17 patients with ST segment elevation in anterior chest leads, but in only three of 21 patients with ST segment elevation in the inferior leads associated with right coronary artery spasm. In the 17, all of whom had spasm of the left anterior descending coronary artery, the sensitivity of ST segment elevation in V5 was only 41%, and that of U wave inversion 71%. U wave inversion without ST segment elevation occurred during attacks in 35% of patients. During the recovery phase, the sensitivity of U wave inversion was 82% in V4 and 65% in V5, though ST segment elevation was absent in both V4 and V5. Thus, inverted U waves without ST segment elevation often appear in marginal ischaemic zones or during the time of recovery from temporary ischaemia. Detection of inverted U waves should aid in the diagnosis of variant angina when only lead V5 is used as a monitor and when electrocardiograms are recorded only during the recovery phase.     

Factors influencing R wave amplitude in patients with ischaemic heart disease.

R wave amplitude changes during exercise have been ascribed to alteration in left ventricular volume and their measurement advocated for the improved diagnosis of coronary disease. The reproducibility of exercise QRS changes and their relation to ST segment depression, respiratory pattern, and left ventricular volume during ischaemia were studied in 10 patients with angina and coronary disease. QRS amplitude was measured in a 16 lead precordial map during three identical exercise tests in each patient and left ventricular volume assessed continuously using gated blood pool imaging with a single scintillation probe during manoeuvres to provoke ischaemia. During exercise, QRS amplitude increased or remained unchanged in four patients and fell in six patients in a consistent manner for each patient. R wave amplitude was not affected by changes in respiratory pattern. R wave amplitude did not alter in 33 of 39 episodes of left ventricular volume increase (mean 32%) or decrease (mean 36%) in end-diastolic counts. These findings suggest that precordial R wave changes during ischaemia are not determined primarily by alteration in left ventricular volume or the respiratory pattern. Though reproducible in each patient and following a definite relation to ST segment depression, the variable directional response during exercise suggest that R wave amplitude changes have little diagnostic value.     

Transition of the ST segment from a J wave to a coved-type elevation before ventricular fibrillation induced by coronary vasospasm in the precordial leads

We describe the case of a 63-year-old man whose electrocardiogram showed transition of the ST segment from a J wave to a coved-type elevation in precordial leads before ventricular fibrillation induced by right coronary artery vasospasm. Simultaneously, the ST segment in inferior leads was gradually depressed with a J wave. Considering the sudden death of his son, induced ventricular fibrillation by programmed electrical stimulation, and modulations of the ST segment in the precordial and inferior leads by pilsicainide, some abnormalities in repolarization associated with Brugada syndrome or early repolarization syndrome might have caused these atypical ST-segment manifestations.     

Influence of R wave analysis upon diagnostic accuracy of exercise testing in women.

Exercise electrocardiography in women with chest pain is associated with a high incidence of false positive ST segment depression. The recent observation that changes in R wave amplitude during exercise can also be used diagnostically may improve the value of stress testing in women. The results of 12 lead treadmill exercise and coronary angiography were reviewed in 62 women, mean age 51 years, presenting with "angina" without previous myocardial infarction. These were compared with exercise results in 14 healthy asymptomatic volunteers with a mean age of 26 years. In addition to conventional ST analysis, R wave amplitude changes during exercise, measured in leads II, III, a VF, and V4 to 6, were examined. While the sensitivity and specificity of ST and R wave changes were similar at about 67%, their combined interpretation was helpful. If both ST and R wave criteria were negative the predictive accuracy for normal coronary angiography was 94% (17/18). Alternatively, in tests showing both ST depression and an abnormal R wave response, coronary angiography was always abnormal (13/13). None of the normal volunteers developed ST segment depression and 93% (13/14) had a normal R wave response. If both were positive, however, coronary angiography was always abnormal (13/13). Although stress test interpretation in women is difficult, R wave analysis is a useful adjunct to ST change and can improve the predictive accuracy of the test in a significant number of patients.     

Prognostic value of Q waves, R/S ratio, loss of R wave voltage, ST-T segment abnormalities, electrical axis, low voltage and notching: correlation of electrocardiogram and left ventriculogram

Data on the correlation of left ventricular segmental wall motion and electrocardiographic findings are, except for Q waves and ST segment elevation, still controversial. Therefore, in addition to Q waves and ST segment elevation, eight features of the electrocardiogram were studied in 265 patients, 61 with normal coronary arteries and 204 with coronary artery disease. Patients with a QRS duration of 0.12 second or greater were excluded. Left ventricular wall motion was assessed in the 30 degrees right anterior oblique and the 60 degrees left anterior oblique projections and analyzed by the Stanford method and a modification of that method, respectively. Asynergy of a particular segment correlated well with the presence of Q waves in the corresponding electrocardiographic lead or leads, but was also found in other segments. There was a significant (p less than 0.001) correlation between the number of leads with Q waves and the degree of extension of asynergy. The R/S ratio in lead V1 and Q waves in lead V6 appeared to be the most informative about the posterior wall. Loss of R wave voltage had a lower predictive value for segmental asynergy than did Q waves in the same lead. Among patients with electrocardiographic findings of an infarct, asynergy was found in 83 to 94%. Patients having Q waves in combination with ST segment elevation manifested more severe asynergy than did patients whose Q waves were not associated with ST elevation. New data are presented for lateral and posterior infarction. Patients having left-axis deviation, low voltage and QRS notching had severe asynergy.(ABSTRACT TRUNCATED AT 250 WORDS)