Electrocardiographic classification of acute coronary syndromes: a review by a committee of the International Society for Holter and Non-Invasive Electrocardiology

Electrocardiographic presentation of global ischemia in acute coronary syndrome predicts poor outcome

BACKGROUND

Global ischemia (GI) electrocardiogram (ECG), wide-spread ST depression with inverted T waves maximally in leads V(4-5), and lead aVR ST elevation (STE), is a marker of an adverse outcome in patients with non-ST elevation acute coronary syndromes (ACS), perhaps because this pattern is indicative of left main stenosis. The prognostic value of this ECG pattern has not been established.

AIMS

The distribution of ECG changes and the prognostic value of the GI ECG were studied.

METHODS

ECGs of consecutive patients admitted with suspected ACS (n = 1,188) were classified into seven ECG categories: STE, Q waves without STE, left bundle branch block, left ventricular hypertrophy, GI ECG, other ST depression and/or T wave inversion, and other findings.

RESULTS

The GI ECG pattern predicted a high rate (48%) of composite end-points (mortality, re-infarction, unstable angina, resuscitation, or stroke) at 10-month follow-up compared to the other ECG categories (36%) (HR 1.78; CI 95% 1.31-2.41; P < 0.001). In multivariate analysis, the GI ECG pattern was associated with a higher rate of composite end-points (HR 1.40; CI 95% 1.02-1.91; P = 0.035). The multivariate analysis furthermore identified age, creatinine level, and diabetes as independent predictors of prognosis.

CONCLUSIONS

The GI ECG pattern predicted an unfavorable outcome, when compared to other ECG patterns in patients with ACS.

Appropriate cardiac cath lab activation: optimizing electrocardiogram interpretation and clinical decision-making for acute ST-elevation myocardial infarction

During the last few decades, acute ST-elevation on an electrocardiogram (ECG) in the proper clinical context has been a reliable surrogate marker of acute coronary occlusion requiring primary percutaneous coronary intervention (PPCI). In 2004, the American College of Cardiology/American Heart Association ST-elevation myocardial infarction (STEMI) guidelines specified ECG criteria that warrant immediate angiography in patients who are candidates for primary PPCI, but new findings have emerged that suggest a reappraisal is warranted. Furthermore, as part of integrated and efficient STEMI systems, emergency department and emergency medical services providers are now encouraged to routinely make the time-sensitive diagnosis of STEMI and promptly activate the cardiac catheterization laboratory (Cath Lab) team. Our primary objective is to provide a practical summary of updated ECG criteria for emergency coronary angiography with planned PPCI, thus allowing clinicians to maximize the rate of appropriate Cath Lab activation and minimize the rate of inappropriate Cath Lab activation. We review the evidence for ECG interpretation strategies that either increase diagnostic specificity for "classic" STEMI and left bundle-branch block or improve diagnostic sensitivity in identifying 4 STEMI-equivalents: posterior MI, acute left main occlusion, de Winter ST/T-wave complex, and certain scenarios of resuscitated cardiac arrest.

Prognostic implications of quantitative ST-segment characteristics and T-wave amplitude for cardiovascular mortality in a general population from the Health 2000 Survey

AIMS

We determined the gender-specific prognostic importance of quantitative measures of the ST segment and T wave in a community cohort.

METHODS

Data were collected from 5613 Finnish individuals. Four electrocardiogram (ECG) lead groups were used: anterior, lateral, inferior, and lead V5. ST-segment depression, determined at four points along the ST segment, and T-wave amplitude were treated as continuous variables in Cox regression analyses.

RESULTS

During a median follow-up period of 72.4 months, 120 cardiovascular deaths were registered. Among women, lateral lead group as well as lead V5 showed highly significant adjusted hazard ratios at all four ST-depression assessment points. This significance was lost in women ≥ 55 years when those with ECG-based criteria of left ventricular hypertrophy (LVH) were excluded. Results for ST-segment depression were not significant among men. As those with LVH were excluded, men ≥ 55 years showed borderline significance. T-wave amplitude did not reach significance among men, while lateral leads and lead V5 bore prognostic information among women.

CONCLUSION

Quantitative ST-segment depression, regardless of the measurement point, allows prediction of cardiovascular death in women within a general population. However, the effect disappears as those with LVH are excluded. This observation highlights the need for consideration of LVH when depressed ST segments are clinically observed.

The absence of the ST-segment elevation in acute coronary artery thrombosis: what does not fit, the patient or the explanation?

In a few patients with acute proximal thrombotic occlusion of the left anterior descending coronary artery (LAD), tall ischemic T waves never evolve into ST-segment elevation. This was recently inaccurately reported as a "novel sign" of proximal LAD occlusion. It has been speculated that the absence of ST-segment elevation could be attributed to the large area of transmural ischemia, the anatomic variant of Purkinje fibers, or to lack of activation of sarcolemal adenosine triphosphate-potassium channels. This electrocardiographic picture was recently explained by changes in the subendocardial but not in the epicardial action potential, suggesting subendocardial ischemia as the underlying mechanism. We present a patient with thrombotic lesion of proximal LAD, static precordial ST-segment depression, and tall T waves who underwent primary percutaneous intervention and stent placement. Surprisingly, total thrombotic stent occlusion on the following day was associated with ST-segment elevation in precordial leads, indeed supporting the concept of the regional subendocardial ischemia that was first described more than a decade ago.

Presence of a critical stenosis in left anterior descending coronary artery alongside a short "P-R" and "Q-T" pattern, in the same electrocardiographic record

The knowledge of the heart and its functions is increasing every day. However, many cardiac dysfunctions remain undocumented. One of them might be the presence of the Wellens' sign, minimally elevated or isoelectric ST segments, and inverted T waves in the precordial leads, without changes in the QRS complex, together with a shortened of "P-R and Q-T intervals" in the same electrocardiographic record. Both patterns are greatly underdiagnosed. The key to an accurate diagnosis of both dysfunctions must begin with a detailed analysis of all the symptoms reported by the patient. The ECG recording provides an almost definitive confirmation: The T-wave characteristics in precordial derivations. The duration of P-R and Q-T intervals.