Atrial pacing and thallium 201 scintigraphy: combined use for diagnosis of coronary artery disease

To evaluate the presence of coronary artery disease (CAD), atrial pacing and thallium 201 scintigraphy were performed in 36 patients with stable angina pectoris who were unable to perform an adequate exercise stress test. All patients underwent cardiac catheterization. Nine patients had previously undergone coronary artery bypass surgery. Significant CAD (one or more lesions greater than or equal to 50%) was present in 33 patients. Atrial pacing produced ischemic ST segment depression (greater than or equal to 1 mm) in 18 (55%) patients with CAD, and angina in 20 patients (61%). As the number of vessels with CAD increased, there was no significant change in the sensitivities of pacing-induced angina or ST segment depression for detecting CAD. In the 3 patients without CAD, ST segment depression occurred in 1 patient and angina in none. Thallium 201 scintigraphy demonstrated perfusion defects in 27 (82%) patients with CAD, with fixed defects seen in 13 studies (39%) and reversible defects in 15 (45%). In the 3 patients without CAD, no perfusion defects were seen. The thallium 201 scan successfully predicted the presence of CAD in patients with single-vessel disease but usually underestimated the number of vessels involved in patients with multivessel disease. Combined sensitivity of pacing-induced ST segment depression and an abnormal thallium 201 scan finding for detecting CAD was 91%. The authors conclude that combined atrial pacing and thallium 201 scintigraphy is a useful test for detecting CAD in patients unable to perform an adequate exercise stress test.     

Effects of ischemia on QT dispersion during spontaneous anginal episodes.

Myocardial ischemia induced by pacing, angioplasty, or stress results in a significant increase in QT dispersion (QTd = QT maximum - QT minimum). This study investigated the effects of ischemia on QTd and the rate-corrected QTd (QT(c)d) during spontaneous anginal episodes in patients with coronary artery disease (CAD). Ninety-five patients with CAD and typical angina pectoris and 15 control subjects complaining of anginalike symptoms were studied. QTd and QT(c)d were calculated from 12-lead surface electrocardiograms recorded during and after the relief of pain. QTd and QT(c)d were significantly higher during the anginal episode (84+/-31 ms and 98+/-51 ms) compared to the painless conditions (69+/-24 ms and 71+/-24 ms) (P = .003 and P = .001 for QTd and QT(c)d, respectively) only in the 57 CAD patients who had a history of an old previous myocardial infarction. QTd and QT(c)d are significantly increased during spontaneous angina in patients with documented CAD and history of previous myocardial infarction.     

平板运动试验中IQTd诊断冠心病的价值

目的　评价用心率调整QTd指标 (IQTd)在平板运动试验中对冠心病的诊断价值。方法　 4 3例患者在冠状动脉造影前行平板运动试验 (ETT) ,测量其运动前、运动中与ST段下移最大时或最大负荷心率时 (无ST段下移者 )QTd、校正QTd(QTdr、QTcdr、QTdp、QTcdp) ,分别计算IQTd和IQTcd。ETT后 1周内行冠状动脉造影 (CAG) ,根据CAG结果分为冠心病 (CAD)组 2 3例和冠状动脉正常 (NCAD)组 2 0例。结果　运动前的QTdr和QTc dr在CAD与NCAD组间无显著差别。在冠状动脉正常组 ,运动过程QTdp和QTcdp无显著增加 ,而在冠心病组QTdp和QTcdp有显著性增加 (P <0 0 0 1)。在运动过程中 ,QTdp、QTcdp、IQTd、IQTcd在CAD与NCAD组间有明显差异。在NCAD组QTdp、QTcdp、IQTd、IQTcd95 %上限值分别为 74ms、86ms、0 .17ms/bpm和0 2ms/bpm。用其界值作为诊断标准 ,其特异性显著高于ST段压低 ,IQTd和IQTcd的敏感性和准确性显著高于ST压低 (P <0 0 5 )。结论　提示IQTd、IQTcd可作为平板运动试验中诊断冠心病敏感、准确和特异的指标     

The protective effect of glucose-insulin-potassium on the response to atrial pacing.

The effects of glucose-insulin-potassium infusion (GIK) on atrial pacing-induced angina, ST depression, abnormal left ventricular end-diastolic pressure during pacing interruption (LVEDPi) and lactate metabolism (L), were studied in 18 patients: ten had angina during pacing = Ischemic group, and eight (5 normals and 3 with coronary artery disease) remained asymptomatic = Nonischemic group. The study consisted of 8-10 minute periods of control, pacing and recovery, before and after GIK. No untoward effects were observed. Comparison of the pacing responses (GIK vs pre-GIK states) showed that during GIK, angina occurred in only 4 patients, while significantly less severe changes were observed in ST depression (1.4 +/-0.5 vs 2.4 +/- 0.4 mm) and LVEDPi (16 +/- 3 vs 23 +/- 3 mm Hg). Lactate extraction was also higher (8.1 +/- 10.9 vs -5.2 +/- 11.1%), but not significantly so, although L became normal in 4 subjects and improved in another. These results indicate that GIK infusion was well tolerated and had a beneficial effect on pacing-induced myocardial ischemia.     

Pacing-induced angina pectoris and induction of ventricular arrhythmias in coronary artery disease

Ischemia caused by rapid pacing during electrophysiologic study could facilitate induction of ventricular arrhythmias. The results of extrastimulation were retrospectively analyzed in 32 patients with coronary artery disease (CAD) without a history of symptomatic arrhythmia. These patients were studied at cardiac catheterization for angina pectoris refractory to medical therapy. Eleven patients (group I) had typical angina during trains of rapid right ventricular pacing (repeated trains of 8 stimuli [mean cycle length (CL) 473 +/- 47 ms]) but were asymptomatic during slower trains (CL 800 +/- 100 ms). Twenty-one patients (group II) had no symptoms with either rapid (CL 448 +/- 51 ms) or slow (CL 688 +/- 105 ms) trains, despite comparable left ventricular function, CAD severity and medication. Effective refractory periods (S1S2) after rapid drive were shorter in group I than in group II patients (225 +/- 9 vs 240 +/- 14 ms, p less than 0.002), but refractory periods during slow pacing were similar (251 +/- 12 vs 253 +/- 17 ms, difference not significant). No patient in either group had sustained arrhythmia (more than 15 beats) induced by single and double ventricular extrastimuli, decrementally applied at the right ventricular apex. The number of extra beats provoked in group I when rapid trains caused angina (4.3 +/- 3.6) was similar to that induced by extra-stimulation after slower pacing without angina (4.4 +/- 3.5) and to that obtained with rapid or slow pacing in group II (3.1 +/- 3.3 and 2.8 +/- 2.2).(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of exercise-induced silent myocardial ischemia in patients with abnormal left ventricular function. A report from the Coronary Artery Surgery Study (CASS) registry

To evaluate the significance of ischemic ST depression without anginal chest pain (silent ischemia) during exercise testing among patients with abnormal left ventricular function, the data on 121 such patients with proven coronary artery disease (CAD) from the Coronary Artery Surgery Study (CASS) registry were analyzed. The patients with silent ischemia (group 1) were compared to: 124 CAD patients with both ST depression and angina (symptomatic ischemia, group 2); 159 CAD patients with neither ST depression nor angina (no ischemia, group 3); and 37 patients without CAD (controls). Survival at 7 years with medical therapy was similar for groups 1 (55%) and 2 (60%), but was substantially better for group 3 (73%, p = 0.001). Among group 1 patients with silent ischemia, survival was related to the severity of CAD (p = 0.001). Patients with silent ischemia and three-vessel CAD had a poor 7-year survival rate (37%) when treated medically. A comparable but non-randomized group of patients with silent ischemia and three-vessel CAD who underwent coronary artery bypass surgery had a much better 7-year survival rate (83%, p less than 0.0001). These results suggest that among patients with CAD and abnormal left ventricular function, silent ischemia adversely affects survival and can identify a higher risk subset of patients whose survival might be improved after coronary bypass surgery.     

Clinical significance of simple heart rate-adjusted ST segment depression in supine leg exercise in the diagnosis of coronary artery disease

To evaluate the clinical significance of simple heart rate-adjusted ST segment depression (delta ST/delta HR) in the diagnosis of coronary artery disease, 42 patients with stable exertional angina underwent supine leg exercise testing and cardiac catheterization. During exercise, heart rate, a multilead electrocardiogram, and pulmonary artery wedge pressure were recorded. The sensitivity and accuracy of the delta ST/delta HR criteria (greater than or equal to 3.0 microV/beat/min) were significantly greater than the conventional analysis of ST segment depression criteria (greater than or equal to 0.2 mV) for detecting three-vessel coronary artery disease at a matched specificity of 72% (100% versus 46%, 81% versus 64%, p less than 0.01). A significant linear correlation was found between maximum pulmonary artery wedge pressure increments during exercise (delta PAWP) or Gensini score and the delta ST/delta HR (delta PAWP: r = 0.51, p less than 0.001; Gensini score: r = 0.47, p less than 0.001). There were no statistically significant differences in the delta PAWP or Gensini score between patients with three-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min and those with one- or two-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min (delta PAWP: 18.1 +/- 2.0 versus 21.9 +/- 3.3, p = NS; Gensini score: 68.5 +/- 6.6 versus 66.3 +/- 11.3, p = NS). These findings demonstrate that delta ST/delta HR is more useful than a conventional analysis of ST segment depression for identifying not only anatomically severe coronary artery disease but also functionally severe coronary artery disease.     

Dynamic changes of QT dispersion as a predictor of myocardial ischemia on exercise testing in patients with angina pectoris.

The difference between the maximum and minimum QT intervals on the standard 12-lead ECG (QT dispersion) may be a significant predictor of serious arrhythmias. Dynamic changes in QTd were determined during exercise-induced ischemia in 15 patients with effort angina (> or = 75% coronary stenosis) and 10 normal individuals. Treadmill exercise testing was performed according to Bruce's protocol and the rate-corrected QT dispersion (QTcd) was calculated using Bazett's formula. The resting QTcd before exercise was similar in the angina patients and the controls. After the first stage of exercise, QTcd was significantly increased in the angina patients (p = 0.035), while it remained near baseline in the controls. Five minutes after completing exercise, QTcd was significantly greater in the angina patients than in the controls (p = 0.011). Furthermore, QTcd values after the first stage of exercise were significantly correlated with the maximum ST depression observed on completing exercise in the angina patients (r = 0.714, p = 0.0028). Because QTd may represent the heterogeneity of ventricular repolarization, its significant exercise-induced increase in the angina patients suggests that myocardial ischemia caused repolarization disorders. The significant correlation between QTcd values after the first stage of exercise (before significant ST depression) and the maximum ST depression on completing exercise suggests that an increase in QTcd preceding ischemic ST depression may predict myocardial ischemia. In addition, even daily activities not causing significant ST changes may increase QTcd and the risk of serious arrhythmia in angina patients.     

Dispersion of the QT interval in unstable angina pectoris

Increased dispersion of the QT interval is a risk factor of sudden cardiac death. In unstable angina pectoris (UA) a few authors described QT dispersion. The aim of the study was to assess QT dispersion in patients with UA in comparison to the healthy subjects and analysis QT dispersion according to the presence during in-hospital stay significant cardiac events like: death due to cardiological causes, myocardial infarction and urgent revascularization. Study group consisted of 54 patients with UA in a class IIIB of Braunwald classification (18 women, 36 men, mean age: 58.2 +/- 9.6 years). In 40 patients after pharmacological treatment stabilization in the first three days of hospitalization was achieved and during in-hospital stay significant cardiac events were not observed--group I. In 14 patients during in-hospital stay significant cardiac events were present, including 5 death due to cardiological causes--group II. During first two days of hospitalization coronary angiography was performed in all patients. The control group comprised 25 healthy subjects (8 women, 17 men, mean age 56.4 +/- 6.1 years). On admission to the hospital in all patients and in control group, using standard 12-leads ECG, following parameters were calculated: QT dispersion (QTd), corrected QT dispersion based on Bazett's formula (QTcd) and QT dispersion ratio (QTdR). In the study group as well as in group I and II values of QTd, QTcd and QTdR were significantly higher than in healthy subjects. In group I all the QT parameters were significantly lower than in group II (QTd: 56.8 +/- 11.2 vs 68.6 +/- 16.6 ms, p = 0.002). The highest value of QT dispersion was found in patients who died during in-hospital stay and it was significantly higher than in survivors (86.0 +/- 13.4 vs 57.1 +/- +/- 10.6 ms, p = 0.004). A cut-off value for QTdR > or = 9% identified patients with high risk of sudden cardiac death. CONCLUSIONS: QT dispersion analysis in unstable angina pectoris allows to distinguish patients according to the risk of sudden cardiac death. Patients with high risk of sudden cardiac death identify the best QTdR.     

多巴酚丁胺负荷试验对劳力型心绞痛QT离散度的影响

目的 :探讨多巴酚丁胺 (Dob)负荷试验对劳力型心绞痛 QT离散度 (QTd)和校正 QT离散度 (QTcd)的影响。方法 :用心电图观察劳力型心绞痛组 (42例 )和非冠心病组 (2 5例 )静息与 Dob负荷作用达终止指标时QTd及 QTcd变化。结果 :组间比较 ,劳力型心绞痛组 QTd及 QTcd静息时略延长 ,但无显著性差异 (均 P >0 .0 5 ) ,达终止指标时 QTd及 QTcd明显延长 (均 P <0 .0 1) ;劳力型心绞痛组组内负荷试验前后比较 QTd及QTcd明显延长 (均 P <0 .0 1)。结论 :劳力型心绞痛在静息时即存在心肌细胞复极不一致 ,Dob负荷作用下 ,心肌细胞复极不一致性更加明显 ,是判断冠状动脉功能的无创性方法     

Value of QT dispersion in the interpretation of treadmill exercise electrocardiograms of patients without exercise-induced chest pain or ST-segment depression

It has recently been reported that increased QT dispersion seen on standard 12-lead electrocardiograms (ECGs) reflects transient myocardial ischemia. The present study investigates whether increased QT dispersion induced by exercise is a useful indicator for detecting significant coronary stenosis in patients who do not have chest pain or significant ST-segment depression in response to exercise. We studied 135 consecutive patients (mean age +/- SD, 55 +/- 9 years; 97 men and 38 women) who complained of anginal chest pain and who did not have exercise-induced chest pain or significant ST-segment depression during treadmill exercise electrocardiography. Coronary angiography was performed in all of patients. Of the 135 patients, 97 had no significant coronary stenosis, 25 had 1-vessel coronary artery disease (CAD), and 13 had multivessel CAD. QT dispersion immediately after exercise was significantly greater in the group with significant coronary stenosis than without significant coronary stenosis (62 +/- 13 vs 40 +/- 14 ms, p <0.0001). When QT dispersion >/=60 ms immediately after exercise was considered a positive result, this indicator had a sensitivity of 74%, a specificity of 85%, and an accuracy of 81% for the diagnosis of significant coronary stenosis. In conclusion, we have shown that QT dispersion immediately after exercise is useful for detecting significant CAD in patients who do not have exercise-induced chest pain or significant ST-segment depression.     

Qualitative and quantitative evaluation of the exercise electrocardiogram in assessing the degree of coronary heart disease

Exercise-induced changes in the ST segments of the electrocardiogram were compared with the results of coronary arteriography in 73 consecutive patients referred for preoperative evaluation of coronary artery disease. Eighteen patients had single-, 25 double-, and 30 triple-vessel disease. Thirteen were taking digitalis alone, 28 were taking beta blockers alone, 21 had beta blockers and digitalis and 11 had no cardiac drugs. Exercise induced elevation of the ST segment in 11 patients, all with a predominant lesion in the left anterior descending coronary artery. ST depression with an upsloping ST segment was observed in patients with one-, two-, and three-vessel disease and it was the most common type of ST change in patients with single-vessel disease. Horizontal ST depression was most common in two-vessel disease and downsloping ST segment in three-vessel disease. There was a good correlation between the number of stenosed vessels and ST changes caused by exercise, expressed as the sum of ST segment displacements in twelve leads recorded immediately after the end of exercise (sigma/ST/) or as ST depression per unit increase in heart rate during exercise ("m" (ST/HR]. The latter was obtained by linear regression of ST displacement and heart rate measured at three or four different workloads in the lead with the greatest displacement of the ST segment. The mean values of sigma/ST/ were 0.58 +- 0.030 mV in single-vessel, 0.97 +- 0.41 mV in double-vessel and 1.58 +- 0. 46 mV in triple-vessel disease. The mean values of "m" (ST/HR) were 0.0024 +- 0.0013 mV X min-1 X beat-1 in single-vessel, 0.0042 +- 0.0012 in double-vessel, and 0.0078 +- 0.0033 in triple-vessel disease. These differences were highly significant (p less than 0.01 - 0.001) and there was only minimal overlap between the single- and triple-vessel groups. Digitalis caused a slight (statistically nonsignificant) increase in sigma/ST/ but not in "m" (ST/HR).     

Evaluation of coronary reserve in angina pectoris with angiographically normal coronary arteries

Coronary reserve was studied: 1) during rapid atrial pacing and then, 2) during dipyridamole infusion (0.6 mg/Kg/4 min) in 3 groups of subjects: 13 patients with angina pectoris and angiographically normal coronary arteries (ANC) with proven myocardial ischaemia during atrial pacing, 15 patients with coronary artery disease (COR) and 17 normal controls with normal coronary angiography and atrial pacing. Coronary sinus flow (QCS) was measured by thermodilution and myocardial metabolism studied by the coefficient of lactate extraction (K). At maximal pacing rates, K remained 15 p. 100 in the control group (average 24 +/- 7 p. 100) but was inversed in the ANC (-3 +/- 10 p. 100) and COR groups (-27 +/- 38 p. 100). The risk in QCS was low in the COR group (+60 +/- 33 p. 100) p less than 0.02, but significant in the ANC group (+104 +/- 57 p. 100) and normal controls (+107 +/- 41 p. 100). Coronary reserve, calculated as the percentage increase in QCS with dipryridamole, was found to be the same in the ANC group (+225 +/- 79 p. 100) as in normal subjects (+191 +/- 81 p. 100) but was low in the COR group (74 +/- 42 p. 100, p less than 0,001). Therefore, no reduction in coronary reserve was shown in patients with angina and normal coronary arteries whilst the myocardial ischaemia in coronary disease does seem to be related to an amputation of the coronary reserve.     

Localization of coronary artery narrowings by applying R-wave amplitude correction to exercise-induced ST depression in angina pectoris and single-vessel coronary artery narrowing

This study investigated whether coronary artery narrowings can be localized by applying R-wave amplitude correction to exercise-induced ST depression in multiple unipolar precordial lead electrocardiography using 20 electrodes covering the left chest wall. Ten normal subjects and 29 patients with stable angina pectoris and single-vessel coronary artery narrowing (greater than or equal to 75% luminal diameter stenosis in only 1-vessel) participated. Of the 29 patients, 5 had left main coronary artery disease (CAD), 14 had left anterior descending CAD, 4 had right CAD and 6 had left circumflex CAD. The exercise-induced ST depression with R-wave amplitude correction was defined as the exercise-induced ST depression divided by the R-wave amplitude. The 20 points of the lead system were divided into 4 areas: the left main, left anterior descending, right and left circumflex coronary arteries. Coronary artery narrowing was supposed to be in an artery corresponding to the area where the maximal value of the exercise-induced ST depression with and without R-wave amplitude correction was situated. By applying R-wave amplitude correction, the diagnostic ability of localization of coronary artery narrowings was improved significantly from 52% to 86% (p less than 0.005). In particular, localization of the left main coronary artery narrowing was correctly diagnosed in 100% (5 of 5) of angina pectoris patients with left main CAD.     

Atrial pacing and thallium-201 scintigraphy in patients with chest pain: correlation with coronary anatomy

Atrial pacing and thallium-201 scintigraphy were performed in 72 patients referred for evaluation of chest pain. Coronary artery disease (CAD) was present in 63 patients, as documented by cardiac catheterization performed at the same time or within 2 months of atrial pacing. Nine patients had no or insignificant (less than 50% stenosis) CAD. The sensitivity of pacing-induced angina for CAD was 51%, and was 49% for ST depression. Specificities were 89% and 78%, respectively. A reversible perfusion defect was seen in 54% of patients with CAD (specificity 89%), and a fixed defect in 29% (specificity 100%). The sensitivity of an abnormal thallium-201 scan (one or more reversible or fixed defects) was 79% (p less than 0.05 compared to angina or ST depression). Combined sensitivity of ST depression and/or an abnormal thallium-201 scan was 87%. There were no significant changes in any of these sensitivities as the number of vessels with CAD increased. Thallium-201 scintigraphy correctly identified 11 of 19 (58%) patients with single-vessel disease as having CAD in only one vessel, but underestimated the extent of disease in all but a few patients with multivessel disease. The sensitivity of perfusion imaging to identify lesions in specific vessels ranged from 27% (circumflex) to 57% (right coronary artery). Specificities were 100% for circumflex, 78% for anterior descending, and 83% for right coronary artery lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

The treadmill exercise score revisited: coronary arteriographic and thallium perfusion correlates.

The treadmill exercise score has been used to stratify patients into low-, moderate-, and high-risk groups. This score is derived from ST segment depression, angina, and exercise duration. To determine the coronary arteriographic and exercise thallium perfusion correlates of the score, we examined the extent of coronary artery disease and exercise single photon emission computed thallium-201 results in 834 patients for whom cardiac catheterization data were available. Of those, 174 had no coronary artery disease, 195 had one-vessel, 246 had two-vessel, and 219 had three-vessel disease. Based on the treadmill exercise score, 369 were in the low-risk, 384 in the moderate-risk, and 81 in the high-risk group. The extent of coronary artery disease was 2.1 +/- 1 diseased vessels in the high-risk, 1.7 +/- 1 in the moderate, and 1.4 +/- 1.1 in the low-risk group (p < 0.01). The extent of the thallium abnormality (maximum number of abnormal segments 120/patient) was 10 +/- 6 in the high-risk, 7 +/- 6 in the moderate, and 6 +/- 5 in the low-risk group (p < 0.05). Based on the extent of coronary artery disease and results of thallium imaging, patients were reclassified into three groups: group 1 had three-vessel disease and/or > or = 10 abnormal segments (n = 387), group 3 had no coronary artery disease or one-vessel disease and less than five abnormal segments (n = 212), and the remaining patients were in group 2 (n = 235).(ABSTRACT TRUNCATED AT 250 WORDS)     

T离散度诊断冠心病心肌缺血的价值

为探讨QT离散度 (QTd)诊断冠心病心肌缺血的价值 ,记录 5 1例冠心病胸痛发作时 ,发作前、后的 12导联同步体表ECG ,测定并计算QTd、校正的QTd(QTcd)及ST段变化 ,判断有关指标诊断冠心病心肌缺血的灵敏性和特异性。结果 :心绞痛 (AP)发作时QTd及ST段改变显著高于胸痛发作前、后的QTd及ST改变 (分别为 80 .1± 2 2 .4vs4 5 .8± 16 .2 ,4 7.8± 17.0 0ms ,P <0 .0 5 ;0 .12± 0 .0 0 8vs 0 .0 3± 0 .0 0 9,0 .0 2± 0 .0 0 7mV)。QTd增大至≥ 80ms、QTd增加≥ 5 0 %、QTd增加≥ 5 0 %兼≥ 80ms、ST段压低或抬高≥ 0 .1mV诊断心肌缺血的灵敏性分别为 86 .2 7%、80 .39%、78.4 3%、5 2 .94 % ;特异性分别为 90 .70 %、79.0 7%、10 0 %、88.37%。结论 :AP发作时QTd显著增大 ,QTd的有关定量指标可作为诊断冠心病心肌缺血的良好指标 ,其中以QTd增加≥ 5 0 %兼≥ 80ms特异性最好。     

Angioplasty decreases prolonged QT dispersion in patients with angina pectoris but not in patients with prior myocardial infarction

BACKGROUND AND HYPOTHESIS: Prolonged QT dispersion (QTd) is shortened by successful percutaneous transluminal coronary angioplasty (PTCA) in patients with ischemic heart disease. Particularly, QTd plays an important role in the prognostication in patients with prior myocardial infarction (MI). However, whether the effect of PTCA on QTd differs in patients with and without prior MI is not clear, and this study sought to clarify this question. METHODS: In 41 consecutive patients with ischemic heart disease, we measured QTd from a routine 12-lead electrocardiogram taken at 72 h before and after successful PTCA. Patients were divided into two groups based on the presence or absence of prior MI: Group 1 consisted of 24 patients with angina (61 +/- 11 years old) without prior MI and Group 2 was comprised of 17 patients (69 +/- 10 years old) with prior MI. QTd was calculated as the difference between the maximum and minimum QT and QT corrected for heart rate (QTc), using Bazett's formula for calculating QTcd. All measurements were obtained manually and blindly. RESULTS: In Group 1, 15 of 24 patients (63%) demonstrated multivessel disease and 16 of 24 (67%) patients had high QTd > 60 ms. Percutaneous transluminal coronary angioplasty decreased QTd and QTcd in Group 1 (QTd, from 83 +/- 35 to 57 +/- 19 ms, p < 0.05 ; QTcd, from 89 +/- 37 to 63 +/- 33 ms, p < 0.05), whereas no changes were observed in Group 2 (QTd, from 73 +/- 25 to 69 +/- 22 ms, NS; QTcd, from 80 +/- 30 to 79 +/- 28 ms, NS). QTd is more sensitive to decrease by successful PTCA in patients with angina than in patients with prior MI. CONCLUSIONS: The effect of successful PTCA on inhomogeneity of ventricular repolarization reflected by QTd in patients with prior MI is different from that in patients without prior MI.     

Changes in QT dispersion during adenosine infusion

BACKGROUND: QT dispersion (QTd) measurement during treadmill stress testing has been to shown to improve the accuracy of exercise electrocardiogram (ECG) in the detection of significant coronary artery disease (CAD). HYPOTHESIS: The aim of this study was to determine whether adenosine-induced changes in QTd could predict significant CAD and to assess its efficacy as a diagnostic index in patients undergoing adenosine stress test. METHODS: QT interval measurements were made in 57 consecutive patients undergoing adenosine sestamibi stress test. Patients with an abnormal stress test underwent coronary angiography. Patients with significant disease by coronary angiography (> 70% stenosis) were classified as having CAD (Group 1), and those with normal stress images and/or normal coronaries by angiography were classified as having no CAD (Group 2). RESULTS: QT dispersion increased from 28.2 +/- 4.5 to 43.8 +/- 4.5 ms with a delta QTd of 15.53 +/- 3.68 in Group 1 (p = 0.001) and from 28.4 +/- 2.6 to 34.8 +/- 2.8 ms with a delta QTd of 6.58 +/- 2.21 ms in Group 2 (p = 0.006). Patients in Group 1 had a significantly higher increase in QTd (delta QTd) than the patients in Group 2 (p < 0.03). Addition of delta QTd (> 10 ms) to the ST depression during adenosine infusion would increase the sensitivity of the ECG from 23 to 65% and decrease the specificity from 91 to 70% for diagnosis of significant CAD. CONCLUSIONS: delta QTd is significantly more prolonged in patients with CAD during adenosine infusion. It increases the sensitivity of the stress ECG in diagnosis of CAD during adenosine infusion when used as an adjuvant index.     

Changes in angina threshold induced by administration of ergonovine maleate during pacing in patients with chronic exertional angina

It is widely accepted that the occurrence of chest pain and/or ST segment elevation during ergonovine testing is a hallmark of abnormal coronary constriction. However, the negativity of this test cannot be considered as an incontrovertible proof of the absence of coronary sensitivity to vasoconstriction. Indeed, it could only indicate that the resulting effect is inadequate to critically reduce coronary blood flow. To test this hypothesis we studied 12 patients with proven coronary artery disease and negative ergonovine test who had complained of chronic exertional angina pectoris and referred variable threshold for the occurrence of pain. They were submitted to atrial pacing (starting from 90 bpm, with 10 bpm increments every 2 min) before (control) and after ergonovine administration (total dose = 0.675 mg). Time, heart rate and rate pressure product were evaluated at the onset of angina and significant ischemia (0.1 mV ST segment depression). After ergonovine, angina was achieved earlier (405 +/- 173 vs 526 +/- 180 sec, p less than 0.005) than during control and at a lower heart rate (116 +/- 15 vs 131 +/- 15 bpm, p less than 0.001) and rate pressure product (15.8 +/- 2.0 vs 18.8 +/- 2.3 X 10(3) U, p less than 0.001). Changes in anginal threshold were widely variable among cases being that the time to onset of pain was dramatically reduced in certain patients but unchanged in one. Similar results were obtained when substituting the ischemic to the anginal threshold. Thus, negativity to ergonovine testing does not imply the absence of coronary constriction which may be revealed when increasing myocardial oxygen demand by atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)