Summation and Cancellation Effects on QRS and ST-Segment Changes Induced by Simultaneous Regional Myocardial Ischemia

Figures

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  Figure 1. Changes in QRS complex duration induced by single and simultaneous occlusion of the left circumflex and right coronary arteries in anesthetized pigs. (A) illustrates the QRS complex widening in ECG leads II, V2 and V8 in a representative case at baseline and after 5-min of occlusion of the left circumflex, right, and double coronary arteries. (B) shows the mean (bars) and standard error (whiskers) of the QRS duration changes from baseline (Δ) in ECG leads II, V2 and V8 recorded in the 4 pigs of the left circumflex and right coronary artery group. Asterisks indicate a p < 0.05 for the QRS duration changes from baseline. LCX, left circumflex coronary artery; RCA, right coronary artery; ms, milliseconds.

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  Figure 2. Changes in QRS complex duration induced by single and simultaneous occlusion of the left anterior descending and left circumflex coronary arteries in anesthetized pigs. (A) illustrates the QRS complex widening in ECG leads II, V2 and V8 in a representative case at baseline and after 5-min of occlusion of the left anterior descending, left circumflex, and double coronary arteries. (B) shows the mean (bars) and standard error (whiskers) of the QRS duration changes from baseline (Δ) in ECG leads II, V2 and V8 recorded in the 4 pigs of the left anterior and left circumflex coronary arteries group. LAD, left anterior descending artery; LCX, left circumflex coronary artery; ms, milliseconds.

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  Figure 3. Changes in QRS complex duration induced by single and simultaneous occlusion of the left anterior descending and right coronary arteries in anesthetized pigs. (A) illustrates the QRS complex widening in ECG leads II, V2 and V8 in a representative case at baseline and after 5-min of occlusion of the left anterior descending, right, and double coronary arteries. (B) shows the mean (bars) and standard error (whiskers) of the QRS duration changes from baseline (Δ) in ECG leads II, V2 and V8 recorded in the 4 pigs of the left anterior descending and right coronary arteries group. LAD, left anterior descending artery; RCA, right coronary artery; ms, milliseconds.

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  Figure 4. Changes in the ST-segment displacement in the surface 15-lead electrocardiogram induced by single and simultaneous occlusion of the left circumflex and right coronary arteries in anesthetized pigs. (A) shows the 15-lead ECG recorded in a representative case at baseline and after single and double 5-min occlusion of the left circumflex and right coronary arteries. (B) illustrates the mean (bars) and the standard error of the mean (whiskers) of the ST-segment displacement recorded in the 15-lead ECG in the 4 pigs of left circumflex and right coronary arteries group. From top to bottom the panels illustrate the ST-segment changes induced after left circumflex, right, and double coronary arteries occlusion. LCX, left circumflex coronary artery; RCA, right coronary artery.

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  Figure 5. Changes in the ST-segment displacement in the surface 15-lead electrocardiogram induced by single and simultaneous occlusion of the left anterior descending and circumflex coronary arteries in anesthetized pigs. (A) shows the 15-lead ECG recorded in a representative case at baseline and after single and double 5-min occlusion of the left anterior descending and left circumflex coronary arteries. (B) illustrates the mean (bars) and the standard error of the mean (whiskers) of the ST-segment displacement recorded in the 15-lead ECG in the 4 pigs of left anterior and left circumflex coronary arteries group. From top to bottom the panels illustrate the ST-segment changes induced after left anterior, left circumflex, and double coronary occlusion. LCX, left circumflex coronary artery; LAD, left anterior descending coronary artery.

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  Figure 6. Changes in the ST-segment displacement in the surface 15-lead electrocardiogram induced by single and simultaneous occlusion of the left anterior descending and right coronary arteries in anesthetized pigs. (A) shows the 15-lead ECG recorded in a representative case at baseline and after single and double 5-min occlusion of the left anterior descending and right coronary arteries. (B) illustrates the mean (bars) and the standard error of the mean (whiskers) of the ST-segment displacement recorded in the 15-lead ECG in the 4 pigs of left anterior descending and right coronary arteries group. From top to bottom the panels illustrate the ST-segment changes induced after left anterior descending, right, and double coronary occlusion. LAD, left anterior descending coronary artery; RCA, right coronary artery.

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  Figure 7. Graphical illustration of the summation and cancellation effects induced by double coronary artery occlusion on the ST-segment changes based on the solid angle theory model. (A) reproduces the mathematical and pictorial characterization of the solid angle theory where the magnitude and direction of the ST-segment shift recorded in an electrode location is determined by: the solid angle (Ω) formed by the projection of the boundaries of the ischemic area to the recording site and by the tissue conductivity (K) and the transmembrane potential gradients generated between the normal (Vmn) and the ischemic (Vmi) areas. Adapted from Holland and Brooks (1977). (B) illustrates the ST-segment cancellation effect in lead V2 in a pig with double occlusion of the left anterior descending and right coronary arteries. (C) illustrates the ST-segment summation phenomenon in lead V2 in a pig with double occlusion of the left circumflex and right coronary arteries. K, tissue conductivity; Vmn, transmembrane potential in the normal tissue; Vmi, transmembrane potential in the ischemic areas; LAD, left anterior descending artery; LCX, left circumflex coronary artery; RCA, right coronary artery.