Electrocardiographic Q-waves inconstancy during thrombolysis in acute anterior wall myocardial infarction

Abnormal Q waves on the admission electrocardiogram of patients with first acute myocardial infarction: prognostic implications

BACKGROUND

Q waves developed in the subacute and persisting into the chronic phase of myocardial infarction (MI) usually signify myocardial necrosis. However, the mechanism and significance of Q waves that appear very early in the course of acute MI (< 6 h from onset of symptoms), especially if accompanied by ST elevation, are probably different.

HYPOTHESIS

This study assesses the prognostic implications of abnormal Q waves on admission in 2,370 patients with first acute MI treated with thrombolytic therapy < 6 h of onset of symptoms.

RESULTS

Patients with abnormal Q waves in > or = 2 leads with ST-segment elevation (n = 923) were older than patients without early Q waves (n = 1,447) (60.6 +/- 11.9 vs. 58.8 +/- 11.9 years, respectively; p = 0.0003), and had a greater incidence of hypertension (34.3 vs. 30.5%; p = 0.05) and anterior MI (60.6 vs. 41.1%; p < 0.0001). Time from onset of symptoms to therapy was longer in patients with Q waves upon admission (208 +/- 196 vs. 183 +/- 230 min; p = 0.01). Peak serum creatine kinase (2235 +/- 1544 vs. 1622 +/- 1536 IU; p < 0.0001), prevalence of heart failure during hospitalization (13.8 vs. 7.0%, p < 0.0002), hospital mortality (8.0 vs. 4.6%; p = 0.02), and cardiac mortality (6.6 vs. 4.5%, p = 0.11) were higher in patients with anterior MI and with abnormal Q waves than in those without abnormal Q waves upon admission. There was no difference in peak creatine kinase, prevalence of heart failure, in-hospital mortality, and cardiac mortality between patients with and without abnormal Q waves in inferior MI. Multivariate regression analysis confirmed that mortality is independently associated with presence of Q waves on admission (odds ratio 1.61; 95% CI 1.04-2.49; p = 0.04 for all patients; odds ratio 1.65; 95% CI 0.97-2.83; p = 0.09 for anterior wall MI.

CONCLUSION

Abnormal Q waves on the admission electrocardiogram (ECG) are associated with higher peak creatine kinase, higher prevalence of heart failure, and increased mortality in patients with anterior MI. Abnormal Q waves on the admission ECG of patients with inferior MI are not associated with adverse prognosis.

Increase in electrocardiographic R-waves after revascularization in patients with acute myocardial infarction

BACKGROUND

The physiological mechanism of the increase in the electrocardiographic (ECG) R-wave voltage after revascularization in patients with acute myocardial infarction (MI) needs to be elucidated.

METHODS AND RESULTS

One hundred and thirty-eight MI patients (83: anterior MI, 45: inferior MI, 10: lateral MI) underwent ECG and echocardiography in both the acute and subacute phases after emergency revascularization, as well as a resting thallium-201/iodine-123 15-p-iodophenyl-3-(R,S)-methyl pentadecanoic acid myocardial scintigraphy in the acute phase. The total sum of the R-wave voltage (SigmaR) was calculated over multiple leads on ECG for each infarcted lesion. Scintigraphic defect on each tracer was expressed as the percentage (%) defect of the total left ventricular (LV) myocardium. The % defect-discordance on both images in the acute phase and the % increase in SigmaR and the absolute increase in LV ejection fraction from the acute to the subacute phase (DeltaEF) were also calculated. The SigmaR in the subacute phase was significantly greater than that in the acute phase (p<0.0001). The % increase in SigmaR significantly correlated with the DeltaEF (r=0.57, p<0.0001). The % increase in SigmaR also correlated with the % defect-discordance (r=0.68, p<0.0001).

CONCLUSIONS

The increase in the ECG R-wave voltage reflects not only the improvement in myocardial perfusion but also the presence of salvaged myocardium after revascularization in acute MI patients.

Electrocardiographic Markers of Reperfusion in ST-elevation Myocardial Infarction

The outcome of patients who fail to reperfuse with thrombolytic therapy or percutaneous coronary intervention (PCI) for ST-elevation acute myocardial infarction (STEMI) may be improved with additional pharmacologic and mechanical interventions such as rescue PCI or intravenous glycoprotein IIb/IIIa infusion. The standard 12-lead ECG is the most commonly available and suitable tool for routine bedside evaluation of the success of reperfusion therapy for STEMI. This article reviews and discusses the current data on the four ECG markers for prediction of the perfusion status of the ischemic myocardium: ST-segment deviation, T-wave configuration, QRS changes, and reperfusion arrhythmias.

Electrocardiographic Diagnosis of ST-elevation Myocardial Infarction

The ECG is an essential part of the initial evaluation of patients who have chest pain, especially in the immediate decision-making process in patients who have ST-elevation myocardial infarction. This article reviews and summarizes the current information that can be obtained from the admission ECG in patients who have ST-elevation acute myocardial infarction, with an emphasis on: (1) prediction of final infarct size, (2) estimation of prognosis, and (3) the correlations between various ECG patterns and the localization of the infarct and the underlying coronary anatomy.

Ischemia-induced ST-segment elevation: classification, prognosis, and therapy

The standard 12-lead electrocardiogram (ECG) remains the most useful tool for the diagnosis, early risk stratification, triage, and guidance of therapy in patients with acute coronary syndromes. However, the initial and the terminal part of the QRS complex, the ST segments, and the T waves are influenced by anatomical and metabolic factors such as the "myocardium at risk" and "severity" and "duration" of ischemia. Moreover, there are complex interactions between all these factors. The ECG can identify potential candidates for reperfusion therapy as well as the completeness and success of reperfusion, whereas it can also identify those patients who will have no benefit from reperfusion because of either late arrival or nonischemic etiologies of ECG changes. These patients may have a "pseudo" ST-elevation acute myocardial infarction (STEAMI) or "pseudo-pseudo" STEAMI. The presence of Q waves and additional ST-segment depression and T-wave inversion on the admission ECG in patients with STEAMI may provide us information regarding the potential myocardial reserves, and various ECG scoring systems are in current use for that purpose. The pattern and timing of changes in Q waves, ST segment, and T waves may all be markers of the patency status of the infarct-related artery. We review and discuss each of the dynamic ECG variables during ischemia and reperfusion: the initial QRS (Q and R waves), the terminal QRS (Sclarovsky-Birnbaum score), the ST segment, and the T waves.

Electrocardiogram of acute ST-elevation myocardial infarction: the significance of the various "scores"

The Electrocardiogram has extensively been used for evaluation and triage of patients with acute chest pain. The clinician admitting a patient with ST elevation acute myocardial infarction should be able to estimate the size and location of the ischemic area at risk, how much of the ischemic myocardium has already undergone irreversible necrosis by the time of presentation, and the "severity of ischemia" (or what is the rate of progression of necrosis as long as ischemia continues). The electrocardiographic variables that are used to make these estimates are the initial portion of the QRS (Q and R waves), the terminal portion of the QRS (the S waves and the J-point), the ST segment, and the configuration of the T waves. This editorial discuss the ability to predict each of the "physiological" parameters using the above mentioned electrocardiographic variables.

The electrocardiogram in ST elevation acute myocardial infarction: correlation with coronary anatomy and prognosis

The electrocardiogram is considered an essential part of the diagnosis and initial evaluation of patients with chest pain. This review summarises the information that can be obtained from the admission electrocardiogram in patients with ST elevation acute myocardial infarction, with emphasis on: (1) prediction of infarct size, (2) estimation of prognosis, and (3) the correlations between various electrocardiographic patterns and the localisation of the infarct and the underlying coronary anatomy.

The use of the electrocardiogram to identify epicardial coronary and tissue reperfusion in acute myocardial infarction

The standard 12-lead electrocardiogram (ECG) gives us crucial information concerning myocardial perfusion and the success of reperfusion therapy for ST elevation acute myocardial infarction. Continuous monitoring has advantages over repeated snapshot recordings. There are four electrocardiographic markers for prediction of the perfusion status of the ischemic myocardium: (1) ST-segment measurements, (2) T-wave configuration, (3) QRS changes, and (4) reperfusion arrhythmias. Complete and stable (> or = 70%) resolution of ST-segment elevation is associated with better outcome and preservation of left ventricular function than partial (30 to 70%) or no (<30%) ST-segment resolution. Early inversion of the T waves after initiation of reperfusion therapy is another marker of myocardial reperfusion and a good prognostic sign. Using standard 12-lead ECG, dynamic changes in Q-wave number, amplitude, and width; R-wave amplitude; and S-wave appearance are detected during reperfusion therapy. However, the significance of these changes has not been clarified. Reperfusion arrhythmias, especially bradycardia and accelerated idioventricular rhythm, are detected occasionally during reperfusion therapy, but the value of reperfusion arrhythmias as a marker of coronary artery patency is still debatable. Dynamic changes in the QRS complexes, ST segments and T waves occur during reperfusion therapy and the days after. Whereas changes in ST-segment amplitude have been extensively studied, the significance of QRS-complex and T-wave changes is less clear, and especially whether changes in the QRS complex and T wave may be complementary and additive to ST-segment monitoring. It has remained unclear whether electrocardiographic signs of reperfusion and reischemia should be used for therapeutic decision making in the clinical setting.

The use of the electrocardiogram to identify epicardial coronary and tissue reperfusion in acute myocardial infarction

The standard 12-lead ECG gives us crucial information concerning myocardial perfusion and the success of reperfusion therapy for ST-elevation acute myocardial infarction. Continuous monitoring has advantages over repeated snapshot recordings. There are four electrocardiographic markers for prediction of the perfusion status of the ischemic myocardium: 1) ST-segment measurements; 2) T-wave configuration; 3) QRS changes; and 4) reperfusion arrhythmias. Complete and stable (> or = 70%) resolution of ST-segment elevation is associated with better outcome and preservation of left ventricular function than partial (30% to 70%) or no (< 30%) ST-segment resolution. Early inversion of the T-waves after initiation of reperfusion therapy is another marker of myocardial reperfusion and a good prognostic sign. Using standard 12-lead ECG, dynamic changes in Q-wave number, amplitude and width, R-wave amplitude and S-wave appearance are detected during reperfusion therapy. However, the significance of these changes have not been clarified. Reperfusion arrhythmias, especially bradycardia and accelerated idioventricular rhythm are detected occasionally during reperfusion therapy, but the value of reperfusion arrhythmias as a marker of coronary artery patency is still debatable. Dynamic changes in the QRS complexes, ST-segments and T-waves occur during reperfusion therapy and the days after. While changes in ST-segment amplitude have been extensively studied, the significance of QRS-complex and T-wave changes are less clear, and especially whether changes in the QRS-complex and T-wave may be complementary and additive to ST-segment monitoring. It has remained unclear whether electrocardiographic signs of reperfusion and re-ischemia should be used for therapeutic decision-making in the clinical setting.