Regional left ventricular function during transient coronary occlusion: relation with coronary collateral flow

Abstract

Objective: To test the hypothesis that regional left ventricular (LV) function during balloon angioplasty is related to the amount of collateral flow to the ischaemic region.

Design: Prospective study.

Setting: Tertiary referral centre.

Methods: In 50 patients with coronary artery disease and without myocardial infarction, regional systolic and diastolic LV function was determined using tissue Doppler ultrasound (TD) before and at the end of a 60 second occlusion of a stenotic lesion undergoing percutaneous transluminal coronary angioplasty (PTCA) through a pressure guidewire. The study population was subdivided into a group with collaterals insufficient (n = 33) and one with collaterals sufficient (n = 17) to prevent ECG ST shifts suggestive of myocardial ischaemia during PTCA. Pulsed TD was performed from an apical window in the myocardial region supplied by the vessel being treated by PTCA. Pressure derived collateral flow index (CFI) was determined by simultaneous measurement of mean aortic (P(ao)) and distal intracoronary occlusive pressures (P(occl)), where CFI = (P(occl) - 8)/(P(ao) - 8).

Results: At 60 seconds of occlusion, several parameters of systolic and diastolic TD derived LV long axis function were significantly different between the groups. Also, there was a significant correlation between regional systolic excursion velocity, early diastolic excursion velocity, regional isovolumetric relaxation time, and CFI.

Conclusion: During brief coronary artery occlusions, regional systolic and diastolic LV function is directly related to the amount of collateral flow to this territory.

Figure 1

Pressure derived collateral flow index (CFI) determination. Simultaneous tracings of surface lead and intracoronary ECG (top), and left ventricular (LVP, mm Hg), mean aortic (P_ao, mm Hg), and mean (left side) coronary occlusive (P_occl, mm Hg) pressure. Phasic P_ao and P_occl are shown on the right. The arrows indicate ST segment elevations during coronary occlusion on intracoronary ECG (insufficient coronary collaterals). CFI is calculated as (P_occl − CVP)/(P_ao − CVP), where CVP is central venous pressure and is assumed to be 8 mm Hg.

Figure 2

Doppler tissue imaging (TD) derived myocardial long axis velocities obtained at the interventricular septum before and at the end of a 60 second occlusion in a patient with collaterals to the left anterior descending coronary artery insufficient to prevent myocardial ischaemia (collateral flow index (CFI) = 0.19). There is a general decrease in the recorded velocities (vertical axis; m/s) during occlusion. CT_r, regional systolic contraction time; IVCT_r, regional isovolumetric contraction time; IVRT_r, regional isovolumetric relaxation time; V_A, late diastolic excursion velocity; V_E, early diastolic excursion velocity; V_+IVCT, positive isovolumetric contraction velocity; V_−IVCT, negative isovolumetric contraction velocity; V_+IVRT, positive isovolumetric relaxation velocity; V_−IVRT, negative isovolumetric relaxation velocity; V_S, systolic excursion velocity.

Figure 3

TD derived myocardial long axis velocities obtained at the interventricular septum before and at the end of a 60 second occlusion in a patient with collaterals to the left anterior descending coronary artery sufficient to prevent myocardial ischaemia (CFI = 0.55). The recorded velocities (vertical axis; m/s) remain unchanged during occlusion.

Figure 4

Correlation between TD derived systolic myocardial long axis velocity indices during occlusion (V_S, cm/s, vertical axis, top; V_+IVCT, cm/s, vertical axis, bottom) and simultaneously obtained CFI (horizontal axis, no unit). There was a significant direct association between the variables. SEE, standard error of estimate.

Figure 5

Correlation between TD derived diastolic myocardial long axis velocity and time indices during occlusion (V_E, cm/s, vertical axis, top; IVRT_r, ms, vertical axis, bottom) and simultaneously obtained CFI (horizontal axis, no unit). There was a significant association between the variables.

Figure 6

Correlation between left ventricular end diastolic pressure obtained during coronary occlusion (LVEDP_occl, mm Hg, vertical axis) and simultaneously measured CFI (horizontal axis, no unit).