On-line vectorcardiography during coronary angioplasty and unstable coronary artery disease
Abstract: This thesis evaluates the usefulness of continuous vectorcardiography (VCG) in patients undergoing elective coronary angioplasty and in patients with unstable coronary artery disease (CAD), for detection and quantitation of myocardial ischemia and for identification of patients at risk of coronary events. The aims were to investigate, whether continuous on-line VCG: 1. gives independent prognostic information regarding death, myocardial infarction (MI) and revascularization, in patients with unstable CAD. 2. during elective angioplasty may identify procedure-related MI. 3. during elective angioplasty gives independent prognostic information as regards repeat revascularization. 4. during elective angioplasty, is different in men and women. 5. during elective angioplasty, relates to systolic and diastolic myocardial velocities determined by tissue Doppler echocardiography. One hundred and fifty patients (age 69±10, 93 men), with unstable CAD, were studied with online VCG recordings for 24 hours. All patients were followed-up while in hospital and 5 to 6 months after discharge. VCG monitoring was performed during elective and initially angiographically successful angioplasty in 192 consecutive patients (age 58±10, 144 men). All patients underwent cardiac enzyme determination before and after the procedure. A 6-month follow-up was obtained. In another 15 patients (age 61±9, 12 men), treated with elective angioplasty, tissue Doppler echocardiography was performed before and at the end of each balloon inflation. The main findings in the different substudies are: 1. VCG monitoring in patients with unstable CAD identifies patients with increased risk of death as well as combined cardiac events. ST Change Vector Magnitude (STC-VM) seems to be the best predictor. The number of STC-VM episodes, with a cutoff value at > 3 STC-VM episodes, is closely related (p<0.0004) to future cardiac events. 2. VCG monitoring during angioplasty may detect patients suffering a procedure-related MI. With a cutoff value at > 200[my]V, maximum STC-VM identifies a procedure-related MI with a sensitivity of 93%, specificity of 59% and a negative predictive value of 99% (P<0.0001). 3. VCG monitoring during angioplasty, may identify patients at increased risk of a revascularization during 6 months follow-up. With a cutoff value at > 240 s, total ischemic time of ST Vector Magnitude (ST-VM) predicts a further revascularization (P<0.01). 4. Women develop VCG signs of more severe myocardial ischemia, have more frequent ischemic episodes and report more severe angina pectoris during the angioplasty procedure than men. 5. STC-VM, during angioplasty, seems to be most closely related to the peak systolic velocity deterioration of the left ventricle, as measured by tissue Doppler echocardiography. In conclusion, VCG monitoring in patients with unstable CAD and during angioplasty gives independent prognostic information. As a prognostic variable, STC-VM seems to be at least as good as ST-VM. Women develop VCG signs of more severe and more frequent myocardial ischemia during the angioplasty procedure than men. STC-VM seems to be the best variable for ischemic monitoring during angioplasty.
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