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Explanation and Significance of the
"Dissociation of ST Segment in V5
and V6 From Lead I and
aVL" Phenomenon

Koracevic, Goran; Erakovic, Vlajko;
Chouliaris, Kostas

Department of Cardiovascular Diseases, Nis, Yugoslavia

Background: So called "left (lateral) leads" usually show striking similarity of QRS morphology.

Objectives: to give an explanation for the new ECG phenomenon "Dissociation of ST segment in V5&V6 from I&aVL and to underline the it's practical importance.

Patients and methods: 114 pts with inferior and lateral wall acute myocardial infarction (AMI) were studied. ST elevation of >1mm in V4R was considered diagnostic for right ventricle (RV) AMI.

Results: ST segment "dissociation" was found in almost half the pts with infero- lateral AMI. Namely, 50 pts had ST in V5 and V6, together with ST in aVL and lead I. LVEF was low (28.9±6.2%) and mortality high (18%) in "ST dissociation" group. Many of them (64%) had specific ECG sign of RV involvement (ST ­ in V4R >1mm). The probable explanation for "ST segment dissociation between V5&V6 from I&aVL": ST­ in V5&V6 is the result of "local" lateral wall lesion (and is not much affected by the current lesion in frontal plane). Logically, we might also expect ST in "other lateral leads" (aVL&I). But, it may not happen, because aVL&I are influenced importantly by the direction of current lesion in frontal plane, which is in RV AMI toward right and down. This is recognized as ST in inferior leads and V4R, together with "mirror image" ST in I&aVL. Thus, "mirror image" (from inferior and RV AMI) overwhelms in aVL and lead I the "local" impact (from lateral AMI).

Conclusions: 1) "ST segment dissociation" between aVL&I vs V5&V6 has high prevalence among infero- lateral AMIs (abouthalf of all infero- lateral wall AMIs). 2) Its practical significance is based upon its predictive capability for poor inhospital prognosis, as well as on being suggestive for right ventricle AMI. 3) Associated right ventricle AMI is responsible for this ECG pattern in majority of pts.



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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
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Scientific Committee
Dr. Armando Pacher
Technical Committee - CETIFAC

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