The relation of localized myocardial lesion size to the QRS complex of vectorcardiographic leads

Effects of localized destructive myocardial lesions on the QRS complex of vectorcardiographic leads was studied by graphic derivation of vectors from the detailed activation sequence of the human heart. Lesions of three sizes were postulated at each of 16 cardiac locations and differences between derived vectors in the presence and absence of lesions determined. At each location there was a near linear relation between lesion size and vector differences. Over different locations, however, there were marked variations in the effects of lesions of a particular size. Variations were due to varied activation patterns within each left ventricular wall since the contribution of each wall (anterior, lateral, posterior and septal) to QRS waveform was nearly identical. Findings suggest that the size of extensive destructive lesions will be well represented by the degree of QRS complex change in vectorcardiographic leads but that vectocardiographic estimates of the size of small lesions or of change of size of either small or large lesions are subject to substantial error.     

Morbidity during five years after myocardial infarction and its relation to infarct size

In 809 patients with a recent myocardial infarction, morbidity during 5-year follow-up was assessed. The overall 5-year mortality rate was 33% (39% in patients with larger infarcts and 26% in patients with smaller infarcts) as judged from maximum serum enzyme activity (p less than .001). In terms of morbidity, no significant association with estimated infarct size was observed. Patients with smaller infarcts tended to have a higher reinfarction rate and were rehospitalized more often, whereas a similar proportion of patients with large and small infarcts developed stroke. Among survivors, chest pain tended to be more common in patients having smaller infarcts, whereas symptoms of dyspnea and claudicatio intermittens were similar in both groups, as were smoking habits, work capability, and varying forms of medication. We thus conclude that during a 5-year follow-up after acute myocardial infarction, mortality, but not morbidity, was related to the original infarct size.     

Nausea and vomiting during acute myocardial infarction and its relation to infarct size and location

Nausea and vomiting occurring during myocardial ischemia is believed to be associated with inferior wall infarction. However, data supporting such an association are limited, and an alternative hypothesis that cardiac vomiting is related to infarct size has also been advanced. The 2 hypotheses were tested in a cross-sectional study of 265 patients consecutively admitted to the coronary care unit. Nausea or vomiting was a good predictor of myocardial infarction (p less than 0.0001). The odds of having an infarction was 3.14 times greater for patients with nausea or vomiting than for those without these symptoms. Nausea was not a good predictor for inferior wall infarction (p = 0.14): 51% of patients with inferior infarcts had nausea or vomiting and 66% with anterior infarcts had these symptoms. Using peak serum creatine kinase level as an index of infarct size, nausea or vomiting was a good predictor of larger infarction. While 55% of all patients with infarction had nausea or vomiting, for patients with infarctions that produced a peak creatine kinase level of more 1,000 IU/liters, 78% had nausea or vomiting. Sex was a marginally important variable. After adjusting for sex, the presence of nausea or vomiting still predicted infarct size (p less than 0.001). Thus, cardiogenic nausea and vomiting are associated with larger myocardial infarctions but do not suggest infarcts in a particular location.     

Ventricular fibrillation threshold in acute myocardial infarction and its relation to myocardial infarct size.

The effect of myocardial infarct size on ventricular fibrillation threshold (VFT) was evaluated by determining changes in VFT during acute myocardial infarction and relating those changes to infarct size. Infarct size was estimated from gross measurement and from serial changes in serum CPK activity in 25 dogs. VFT reduction correlated well with gross infarct size (r=0.92). This suggests that the severity of electrical instability during AMI is related to the size of the developing infarct, and that appropriate therapeutic interventions to reduce infarct size during this time may also render the heart more electrically stable.     

Comparison of infarct size changes with delayed contrast-enhanced magnetic resonance imaging and electrocardiogram QRS scoring during the 6 months after acutely reperfused myocardial infarction

Introduction

Magnetic resonance imaging using the delayed contrast-enhanced (DE-MRI) method can be used for characterizing and quantifying myocardial infarction (MI). Electrocardiogram (ECG) score after the acute phase of MI can be used to estimate the portion of left ventricular myocardium that has infracted. There are no comparison of serial changes on ECG and DE-MRI measuring infarct size.

Aim

The general aim of this study was to describe the acute, healing, and chronic phases of the changes in infarct size estimated by the ECG and DE-MRI. The specific aim was to compare estimates of the Selvester QRS scoring system and DE-MRI to identify the difference between the extent of left ventricle occupied by infarction in the acute and chronic phases.

Methods

In 31 patients (26 men, age 56 ± 9) with reperfused ST-elevation MI (11 anterior, 20 inferior), standard 12-lead ECG and DE-MRI were taken from 1 to 2 days (acute), 1 month (healing), and 6 months (chronic) after the MI. Selvester QRS scoring was used to estimate the infarct size from the ECG.

Results

The correlation values between infarct size measured by DE-MRI and QRS scoring range from 0.33 to 0.43 higher for anterior than inferior infarcts. The infarct size estimated by QRS scoring was larger (about 5% of the left ventricle) than infarct size by DE-MRI acute and 1 month, but at 6 months, there was no difference. In about half of the patients, the QRS score agreed with DE-MRI in change of infarct size from acute to 6 months.

Conclusion

In conclusion, the Selvester QRS scoring system is in half of the patients with reperfused first time MI in good accordance with DE-MRI in identifying a decrease or no change in the extent of left ventricle occupied by infarction in the acute and chronic phases.     

Continuous vectorcardiographic changes in relation to scintigraphic signs of reperfusion in patients with acute myocardial infarction receiving thrombolytic therapy

Objectives. Changes in the electrical activity of the heart reflecting the infarct process can be recorded by continuous vector-ECG, a method which is now clinically available for cardiac supervision. Shifts of the ST-segment and QRS-vector reflect ischaemia and necrosis of the myocardium. Continuous vector-ECG changes were evaluated against myocardial scintigraphy in 18 patients with acute myocardial infarction treated with streptokinase in order to study the impact of improved myocardial perfusion. Design. Myocardial perfusion was analysed with ⁹⁹Tc^m-Sestamibi (Cardiolite, DuPont Scandinavia AB, Kista, Sweden) single photon emission computerized tomography (SPECT). Registrations were performed before and after thrombolysis in order to estimate the amount of myocardium with impaired perfusion initially (threatened myocardium) and the degree of perfusion improvement in this myocardial area. X, Y, Z vectors were registered continuously by Frank leads (Ortivus Medical, Täby, Sweden). QRS-vector difference, and the time to plateau phase and the ST-vector magnitude were used as a measurement of ischaemia and size of the myocardial infarction. Results. In seven out of 11 patients treated within 3 h of onset of symptoms, an improvement in myocardial perfusion in the initially hypoperfused areas was achieved in contrast to none of the seven patients treated >3 h after onset of pain (P<0.05). In the whole patient material, there was a negative correlation between the time to plateau level for the QRS-vector and the improvement in myocardial perfusion (r=-0.53, P<0.05). Among patients treated within 3 h, there was a negative correlation between the plateau level for the QRS-vector magnitude compared to the improvement in myocardial perfusion (r=-0.61, P<0.05) and a negative correlation between the plateau level and the myocardial perfusion level after therapy (r=-0.69, P<0.05). In these patients, there were also negative correlations between the maximal ST-vector magnitude and the myocardial perfusion both before and after thrombolysis (r=-0.81, P<0.05 and r=-61, P<0.05, respectively). Conclusion. Patients with marked improvement in myocardial perfusion indicating successful thrombolysis reach their plateau levels of the QRS-change faster and have lower total QRS-vector differences than patients without successful thrombolysis as reflected by myocardial scintigraphy. Patients with a high ST-vector magnitude have low perfusion levels both before and after therapy indicating a pronounced ischaemic damage of the myocardium. Thus, VCG-changes reflect impairment in myocardial perfusion during acute myocardial infarction.     

Plasma CK-MB activity and QRS score in estimating acute myocardial infarct size

Comparison of the peak value of plasma isoenzyme MB of creatine kinase (CK-MB) and the modified Selvester QRS score system from the standard 12-lead electrocardiogram in estimating acute myocardial infarct size and predicting hospital prognosis was performed in 52 patients with initial acute myocardial infarction (AMI). A correlation coefficient (C.C.) of 0.51 in all these patients was found. The C.C. in the patients with anterior AMI (n = 22, r = 0.64) is larger than that in inferior AMI (n = 30, r = 0.34). The prognostic value of the two methods are different. Peak CK-MB activity could predict hospital mortality and morbidity (serious arrhythmia or/and Killip AMI classification more than class III) for both anterior and inferior AMI; however, the QRS score system was significant only for anterior AMI. The clinical significance of a high ratio of peak CK-MB activity to QRS score was discussed briefly.     

Evaluation of serial QRS changes during acute inferior myocardial infarction using a QRS scoring system

The evolution of changes in the QRS complex during the initial 3 days after the onset of an initial inferior myocardial infarction (MI) was studied in 82 consecutive patients. Each patient's standard 12-lead electrocardiogram was assigned points (a QRS score) according to the absolute duration of the Q and R waves and the amplitude ratios of R-to-Q and R-to-S waves. This QRS score has been demonstrated to correlate (r = 0.74) with the anatomic extent of single inferior MI. By this system, 43 patients (53% of the study group) had an initial electrocardiogram that registered a score of 0 and developed QRS points only after admission. The QRS scores of 18 additional patients (22% of the study group) changed after admission. Forty-nine score changes were noted on Day 2 and 18 on Day 3. All of these changes resulted in an increased QRS score. Alteration of the QRS complex during initial inferior MI evolves over 2 to 3 days in many patients. There is a distinct pattern to this evolution, which results in sequential increases in a QRS score based upon electrocardiographic indicators of the extent of myocardial necrosis. This QRS scoring system might be applied to evaluate clinically interventions aimed at limiting the extent of necrosis in patients with initial acute inferior MI.     

Correlation between electrocardiographically and enzymatically estimated infarct size and its relation to clinical course in inferior myocardial infarction

In 194 patients with inferior wall acute myocardial infarction (MI) defined from ECG, the initial ST elevation and final Q- and R-wave changes in leads II, III and aVF were related to peak serum enzyme (heat stable lactate dehydrogenase) activity. Positive correlations were observed between initial ST elevation and peak LD (r = 0.54; p less than 0.001) and between peak LD and the final Q- and R-wave changes (r = 0.45; p less than 0.001). Peak LD activity was strongly related to the incidence and severity of congestive heart failure, and to mortality after 90 days and 2 years. A similar relationship could not be demonstrated between ECG findings and clinical outcome.     

Evolution of left ventricular ejection fraction and its relationship to infarct size after acute myocardial infarction.

OBJECTIVES: The aim of this study was to investigate the evolution of left ventricular (LV) function and infarct size in patients with acute myocardial infarction (MI) treated with primary coronary stenting. BACKGROUND: Little evidence exists on the relationship between LV function and evolution of infarct size after MI. METHODS: This study included 626 patients with first acute MI who underwent 2 angiographic and 3 scintigraphic examinations within 6 months after the acute event. Angiographic left ventricular ejection fraction (LVEF) at baseline and at 6-month angiography, and perfusion defects before intervention and at 7- to 14-day and 6-month scintigraphy after intervention were measured. An analysis of 3-year follow-up was performed. RESULTS: Scintigraphic perfusion defect (median [25th, 75th percentiles]) was 24.6% [14.0%, 41.0%] of LV before intervention; it was reduced to 11.0% [5.0%, 24.0%] of LV at 7 to 14 days and further to 8.0% [2.0%, 19.0%] of LV at 6 months (p < 0.001). The LVEF was 51.6 +/- 12.0% before intervention and increased to 57.4 +/- 12.8% at 6 months (p > 0.001). Independent predictors of LVEF change were baseline LVEF (p < 0.001), initial perfusion defect (p < 0.001), early reduction in perfusion defect (p < 0.001), late reduction in perfusion defect (p < 0.001), peak creatine kinase-MB (p < 0.001), and smoking (p = 0.05). Three-year mortality was 1.2% in patients with improved LF function versus 5.6% in patients with worsened LV function (relative risk 0.29, 95% confidence interval 0.09 to 0.90; p = 0.03). CONCLUSION: Patients with acute MI show an improvement in LV function and a reduction in infarct size within 6 months after coronary reperfusion. This improvement is associated with better long-term survival.     

快速洋地黄类药对犬实验性急性心肌梗死早期血流动力学、梗死面积的影响

探讨洋地黄类药物对急性心肌梗死早期血流动力学、梗死面积的影响。方法３０只健康种状随机分为对照组及哇巴因组,结扎左冠状动脉前降支,造成实验性ＡＭＩ模型,通过心内导管及主动脉电磁流量计测量结扎前后、用药前后两组血流动力学,冠状动脉流量。心肌Ｎ－ＢＴ染色测量两组梗死面积。