The Significance of a Wide TsÊ Loop

When is the vectorcardiogram superior to the scalar electrocardiogram?

The clinical usefulness of the vectorcardiogram is well documented by the numerous reports published in the last 3 decades. It has been found more reliable than the electrocardiogram for the diagnosis of atrial enlargement and right ventricular hypertrophy. It is more sensitive than the electrocardiogram in the recognition of myocardial infarction, especially if the infarction is inferior or if it occurs in the presence of left bundle branch block or left anterior hemiblock. It is helpful in the diagnosis of ventricular pre-excitation and in the localization of the bypass tract. Some repolarization abnormalities are more clearly demonstrated by the vector display. However, some information, such as that on cardiac chamber size and myocardial damage, can also be obtained by other noninvasive tests that are often performed on the same patients. With the increasing awareness of cost-effectiveness of various laboratory procedures in medicine, the vectorcardiogram should no longer be considered a routine cardiac test and should be requested only for a specific clinical purpose. When properly utilized, vectorcardiography should remain a valuable diagnostic as well as teaching tool.

T loop in posterior myocardial infarction: a useful clue to vectorcardiographic diagnosis

In order to differentiate posterior (posterolateral) myocardial infarction (PMI) from the anterior shift of the QRS loop in "normal variant" cases using a vectorcardiogram, the T loop as well as the QRS loop in the transverse plane (TP) were analyzed in 34 elderly Japanese males with angiographically-proven PMI and in 197 elderly Japanese males with normal coronary arteries and ventricles. T loops in the TP were longer, narrower and more anterior in PMI cases. After this analysis, we propose new criteria for PMI: (A and B) A: maximal T vector equal or anterior to 60 degrees in TP B: at least two of the following three: maximal QRS voltage/maximal T voltage in TP equal to or less than 3.0; QRS-T angle equal to or less than 75 degrees in TP; width/length of T equal to or less than 0.15 in TP. These new criteria for PMI are more specific (p less than 0.01) and more sensitive (p less than 0.05) than Hoffman's criteria.

Comparison of scalar and vector electrocardiographic diagnosis and localization of myocardial infarction

A prospective study was made of 80 patients during typical clinical episodes of acute myocardial infarction with biochemical and scalar electrocardiographic confirmation. Nine patients had bundle-branch block and 12 had had previous episodes of myocardial infarction. Serial electrocardiograms and vectorcardiograms were recorded during the first week in hospital. The most striking finding was that in more than half the cases there was disagreement between the electrocardiogram and vectorcardiogram in the localizationof infarction. The earliest evidence of infarction in the electrocardiogram is often restricted to ST and T changes though in the corresponding vectorcardiograms evidence of infarction may be present in the QRS loop. In those cases in which both electrocardiogram and vectorcardiogram show QRS abnormalities these are frequently detected earlier in the vectorcardiogram, but the converse is rare.

Vectorcardiographic T loop analysis in ischaemic heart disease

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