Usefulness of Seismocardiography for the Diagnosis of Ischemia in Patients with Coronary Artery Disease

Background: Seismocardiography (SCG) is a useful method for the detection of exercise‐induced changes in cardiac muscle contractility which may occur during myocardial ischemia. The aim of this study was to compare the diagnostic accuracy of SCG with electrocardiographic exercise test (ETT) for diagnosis of ischemia in patients with angiographically proved coronary artery disease (CAD). Methods: Seventy‐seven male patients with CAD without myocardial infarction (MI), mean age 51 ± 9 years, were subjected to SCG and ETT. A gender‐matched control group consisted of 30 healthy volunteers aged 34 ± 7 years. SCG was done simultaneously with resting supine 12‐lead electrocardiography before and immediately after a symptom‐limited ETT. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of SCG were compared with ETT. Moreover, the diagnostic accuracy of both the methods was compared, with coronary angiography being the reference for the analysis. Results: SCG was more sensitive (61.1% vs 44.2%, P < 0.05) and accurate (70% vs 61%, P < 0.05) method for detecting ischemia caused by coronary stenosis ≥50%, at least in one coronary artery compared to the ETT. However, ETT had better specificity than SCG (82.4% vs 76%, P < 0.05). The PPV and NPV of SCG were significantly better than those obtained with ETT (77.9% vs 76%, P < 0.05 and 63.4% vs 53.8%, P < 0.05, respectively). Moreover, the concordant results of SCG and ETT improved the diagnostic accuracy of both methods. Conclusions: SCG appeared to be more sensitive for detecting ischemia caused by more than ≥50% stenosis of the main coronary artery compared to an electrocardiographic stress test. SCG was a useful ETT adjunct for selecting patients requiring coronary angiography.     

Role of coronary spasm for a positive noninvasive stress test result in angina pectoris patients without hemodynamically significant coronary artery disease

BACKGROUND: A positive noninvasive stress test result is often considered as a false-positive indicator of coronary artery disease (CAD) when coronary angiography reveals no hemodynamically significant CAD. METHODS: From January 2001 through December 2004, 5474 patients scheduled to undergo exercise electrocardiogram (ECG) [exercise ECG without imaging or exercise ECG with thallium-201 (201Tl) single photon emission tomography (SPECT)] or dipyridamole 201Tl tomography at our outpatient clinic because of chest oppressive sensation were included in this prospective study. Coronary angiography was performed when a noninvasive test result was positive for ischemia or when ischemic chest pain was suspected. Intracoronary methylergonovine testing was performed when spastic angina was suspected and coronary angiography showed no hemodynamically significant CAD. RESULTS: Noninvasive stress testing was positive in 113 (67%) patients with coronary spasm. Of the 53 patients who had positive exercise ECG (exercise ECG with or without imaging), ST depression was found in 50 patients and ST elevationin in 3 patients. Multivessel spasm was found in 6 (15%), 6 (15%), and 7 (21%) of the patients with a positive result on exercise ECG without imaging, exercise ECG with 201Tl SPECT, and dipyridamole 201Tl SPECT, respectively. There was no significant difference in the results of noninvasive stress testing and the number of vessels with coronary spasm (1-vessel spasm versus multivessel spasm) among these 3 noninvasive stress testing groups. CONCLUSION: Intracoronary ergonovine testing induced coronary spasm in over 50% of patients who had suspected ischemic chest pain, a positive noninvasive stress test, and no hemodynamically significant CAD.     

The detection of myocardial ischemia by thallium-201 myocardial scintigraphy in patients with multiple coronary arterioventricular connections.

The question of whether myocardial ischemia could be induced in 5 patients with multiple coronary arterioventricular connections by thallium-201 (201Tl) exercise stress myocardial scintigraphy was investigated. Both ST-T changes on ECG and transient myocardial perfusion defects in myocardial scintigrams were observed in 2 patients (40%). In previous reports, all multiple coronary arterioventricular connections, which were shown in angiograms, have been regarded as either Thebesian veins or embryonic sinusoids. However, it is unlikely that Thebesian veins cause myocardial ischemia judging from anatomy. If the vessels cause myocardial ischemia, they should be regarded as multiple coronary arterioventricular fistula. Angiography itself cannot differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids. Exercise stress myocardial scintigraphy has a high potential to detect myocardial ischemia due to intracoronary steal. Exercise stress myocardial scintigraphy was used to demonstrate myocardial ischemia in multiple coronary arterioventricular connections. It is concluded that exercise stress myocardial scintigraphy is a reliable test to differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids in clinical practice.     

Changes in plasminogen activator inhibitor 1 and tissue-type plasminogen activator during exercise in patients with coronary artery disease

As depressed fibrinolysis is implicated in the pathogenesis of coronary artery disease, we have studied the activation of fibrinolysis during maximal, symptom-limited exercise in a group of 68 men. After exercise they were divided, according to their coronary angiography and exercise 201Tl emission computed tomography results, into three groups. Group 1: persons with normal exercise 201Tl emission computed tomography results and no underlying diseases who served as controls; group 2: patients with coronary artery disease without exercise-induced myocardial ischemia, and group 3: patients with coronary artery disease with transient, exercise-induced myocardial ischemia. Before and at peak exercise we measured the plasminogen activator activity (PAA) in the euglobulin fraction of plasma by an amidolytic method and the concentrations of tissue plasminogen activator (t-PA), activator-inhibitor complex - plasminogen activator inhibitor 1 (PAI-1) complexed with t-PA - and total PAI-1 by enzyme immunoassay. The concentration of free PAI-1 in plasma was calculated by subtraction of the concentration of activator-inhibitor complex from that of total PAI-1. Under basal conditions, group 3 had significantly higher free and total PAI-1 levels than group 1. There were no statistically significant differences between the three groups in PAA, t-PA, and activator-inhibitor complex levels. At peak exercise, group 1 showed the highest release of t-PA accompanied with highest increases in PAA as well as in activator-inhibitor complex, the proportion of released t-PA antigen not bound to PAI-1 being highest in group 1. Free PAI-1 decreased significantly, but there were no differences between individual groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Value of myocardial scintigraphy using T1-201 in the diagnosis of ischemic heart disease

The results of ECG, bicycle ergometry (BEM) and myocardial 201Tl scintigraphy at rest and during BEM exercise were evaluated in 78 male and 24 female coronary patients as well as 18 normal controls. Scintigraphy during the BEM test is shown to be capable of detecting areas of transient myocardial ischemia. The sensitivity of the BEM test and myocardial scintigraphy was 83 and 91%, respectively, in detecting transient myocardial ischemia. Myocardial 201T1 scintigraphy should be conducted where other investigations, used for the diagnosis of coronary disease, yield little information: in patients with angiographically-intact coronary arteries and in cases of atypical clinical appearance of coronary heart disease.     

Reevaluation of routine invasive strategy versus noninvasive testing following uncomplicated ST-elevation myocardial infarction

BACKGROUND AND AIMS: While current guidelines recommend a selective invasive approach after low-risk ST-elevation myocardial infarction (STEMI) treated by thrombolysis, based on noninvasive identification of patients with residual or inducible myocardial ischemia, in many instances physicians employ a strategy of routine angiography. The present study was undertaken to reexamine the correlation between noninvasive testing and coronary angiography in patients recovering from uncomplicated STEMI with regard to detection and management of residual infarct artery stenosis and to identify patients with multivessel (MVD) or high-risk coronary disease. METHODS: We prospectively performed predischarge exercise testing (ETT) and myocardial perfusion scintigraphy (MPS) prior to routine predischarge coronary angiography in 83/276 consecutive STEMI patients, who after treatment with initial and early thrombolysis, were defined as low risk by ACC/AHA risk classification. RESULTS: ETT was positive for myocardial ischemia in 11/43 (26%) patients with single-vessel disease (SVD) and 11/22 (50%) patients with MVD, but normal or nondiagnostic in the remainder. MPS revealed significant reversible perfusion defects in 13/40 (32%) patients with SVD and 13/22 (59%) patients with MVD. A selective strategy of ETT followed by MPS for nondiagnostic ETT missed residual infarct-related artery stenosis and/or MVD in 31/81 (38%) of the cohort. Among patients who may not otherwise have been referred for angiography, severe (> or =70%) residual stenosis of the infarct-related artery was present in 56% and MVD in 16%. CONCLUSIONS: Early predischarge ETT and/or MPS had limited sensitivity for the detection of coronary disease in low-risk post-STEMI patients. The study supports a simpler strategy of routine coronary angiography in most patients after low-risk STEMI.     

平板运动试验时的QT离散度诊断冠心病的价值

为了解ＱＴ离散度（ＱＴｄ）在运动试验中的变化对冠心病心肌缺血的诊断价值，对３０例临床诊断或疑诊为冠心病的病人先后行平板运动试验（简称运动试验）及冠状动脉（简称冠脉）造影检查。１７例运动试验阳性者中１０例确诊为冠心病；１３例运动试验阴性者中１０例冠状动脉正常。运动试验诊断冠心病的敏感性７６．９％、特异性５８．８％、准确性６６．７％。冠心病组与冠脉正常组运动前、中、后ＱＴｄ分别为４６．２５±２０．１３ｍｓ、７１．９２±２０．３７ｍｓ、５１．２５±１４．４８ｍｓ及３２．３５±６．６４ｍｓ、３０．８８±９．２３ｍｓ、２９．３８±８．５４ｍｓ，两者比较，Ｐ均＜０．０１。冠心病组运动前、后与运动中ＱＴｄ比较，差异有显著性，Ｐ＜０．００５；而冠脉正常组ＱＴｄ变化无显著性。以运动中ＱＴｄ≥６０ｍｓ为异常，诊断冠心病的敏感性为９２．３％、特异性１００％、准确性９６．７％。提示运动试验中ＱＴｄ增加可作为诊断冠心病心肌缺血的敏感而特异的指标     

Usefulness of diastolic time measured on electrocardiogram to improve sensitivity and specificity of exercise tolerance tests

The current exercise tolerance test (ETT) criteria predominantly assess changes in ST-segment deviation (i.e., a systolic component of the cardiac cycle). Because diastolic dysfunction precedes that of systolic dysfunction during myocardial ischemia and most coronary flow is diastolic, the addition of electrocardiographic markers of diastolic time might improve the ETT sensitivity and specificity for detecting significant coronary artery disease. Among consecutive patients who had an ETT and subsequently underwent coronary angiography, we evaluated the diastolic time by assessing the TP and TQ segments and TP/RR and TQ/RR ratios in each ETT stage. Coronary artery disease was defined angiographically as significant (≥70% lumen occlusion), intermediate (>50% but <70% lumen occlusion), or nonsignificant (≤50% lumen occlusion). Of the 48 study patients, hypertension and hyperlipidemia appeared highly prevalent. TP, TQ, TP/RR, and TQ/RR correlated significantly with RR and changed with each ETT stage. Although TP and TQ were not significantly associated with significant coronary artery disease, TP/RR and TQ/RR proved to be, particularly beyond stage 2. When TQ/RR of ≤0.39 and TP/RR of ≤0.13 were used, their individual sensitivities and specificities were reasonably comparable to that of traditional ETT criteria (79% sensitivity and 44% specificity at our institution). Adding TQ/RR of ≤0.39 and/or TP/RR of ≤0.13 to existing ETT criteria improved its sensitivity to 100% and specificity to 86%. In conclusion, the addition of diastolic time indexes of TP/RR and TQ/RR significantly improved the overall ETT diagnostic value above the guideline-oriented, perhaps "traditional," criteria for the diagnosis of myocardial ischemia. Such parameters should be widely investigated further for clinical accuracy and compatibility.     

ECG Diagnosis of Coronary Artery Disease

Objective: In order to assess the diagnostic accuracy of ST depression in the diagnosis of coronary artery disease (CAD) in patients with suspected myocardial ischemia we compared ST depression in 3-lead ambulatory ECG (AECG) with that of exercise tolerance testing (ETT). Methods: Significant coronary artery stenosis in coronary angiography was used as a standard reference. ST analysis could be performed in 106 of the investigated 113 patients, all with suspected CAD. One person with left bundle branch block was excluded from the ST analysis, and six persons could not perform ETT. Results: Seventy-eight of the 106 patients had at least one significant stenosis (> 70% narrowing) and 28 had no stenosis according to coronary angiography. The sensitivity for AECG was 62% and for ETT it was 63%, the specificity for AECG was 79% and for ETT the specificity was 57%. The accuracy for AECG was 66%, and for ETT it was 61%. We also evaluated late potentials (LPs) from the AECG tapes in order to correlate LP to left ventricular function (LVF), myocardial infarction (Ml), and/or CAD. We found that LP correlates better to advanced CAD than to Ml or LVF. Conclusion: The accuracy of ST diagnosis of CAD in patients with suspected myocardial ischemia using AECG was equal to that of a maximal ETT. LP finding from an AECG tape may support the argument for CAD in patients with ST depressions at AECG.     

Effects of exercise training on myocardial fatty acid metabolism in rats with depressed cardiac function induced by transient ischemia.

The effects of exercise training on metabolic and functional recovery after myocardial transient ischemia were investigated in a rat model. Male Wistar Kyoto rats were subjected either to a 30-min left coronary artery occlusion followed by reperfusion or to a sham operation. At 4 weeks after operation, the rats were randomly assigned either to sedentary conditions or to exercise training for 6 weeks. In the ischemic rats, pinhole SPECT (single photon emission computed tomography) imaging with thallium-201 (201Tl) and 123I-(rho-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) showed a reduction of both myocardial perfusion and fatty acid metabolism in the risk zone of the left ventricle (LV). The LV was dilated and the ejection fraction was decreased after ischemic injury. The severity score showed a significant decrease on both 201Tl and BMIPP (201Tl, from 19.9+/-2.7 to 17.0+/-2.2, p<0.05; BMIPP, from 21.5+/-2.4 to 18.6+/-1.9, p<0.05) after exercise training in the ischemic trained rats, but did not change significantly in their sedentary counterparts. Plasma levels of free fatty acids normalized in the ischemic trained rats, but elevated in the ischemic sedentary rats (0.53+/-0.05 vs 0.73+/-0.06 mmol/L, p<0.05). Furthermore, the trained rats had a significant increase in LV stroke volume (0.25+/-0.02 vs 0.21+/-0.01 ml/beat, p<0.05) and adaptive cardiac hypertrophy. These findings demonstrate that adaptive improvements in myocardial perfusion, fatty-acid metabolism and LV function were induced by exercise training after transient ischemia.     

Exercise-triggered transient R-wave enhancement and ST-segment elevation in II, III, and aVF ECG leads: a testament to the "plasticity" of the QRS complex during ischemia

We describe a patient with coronary artery disease who showed transiently augmented R-waves in his electrocardiogram (ECG) during the course of an exercise treadmill test (ETT), an ECG pattern occasionally associated with the hyperacute phase of myocardial infarction and variant angina. This change in the R-waves was noted in II, III, and aVF ECG leads and was associated with ST-segment elevation; both changed gradually and were normalized during the recovery period. Cardiac enzymes after ETT were negative, and arteriography revealed 3-vessel coronary artery disease, with a completely occluded right coronary artery. The ventriculogram showed very mild hypokinesis of the inferior left ventricular wall, while the global ejection fraction was 75%. These ECG changes, noted previously during ETT in precordial ECG leads, are herein reported to occur also in II, III, and aVF ECG leads. The generation of these ECG changes, which hinges upon a late unopposed depolarization occurring in the course and at the site of severe ischemic injury, constitutes a transient focal ventricular conduction abnormality.     

Early redistribution of thallium-201 after temporary ischemia

To define the time course of redistribution of thallium-201 (201Tl), ischemia was induced in seven pigs by temporary occlusion of the circumflex coronary artery. After 1 1/2 min of occlusion 201Tl and labeled microspheres were injected into the left atrium. Flow was re-established 4 min after occlusion. Prior to reflow, the relative activities of 201Tl and microspheres in the ischemic area were similar, but as early as 5 min after reflow the relative 201Tl activity was considerably higher than the relative microsphere activity and from 15 to 105 min after reflow, relative 201Tl activity (averabe 69% of that in normal myocardium) continued to be higher than relative microsphere activity (average 6% of normal). Myocardial arteriovenous differences for 201Tl were followed sequentially after 201Tl injection in normal dogs and in dogs with temporary coronary occlusions. The results suggested both loss of 201Tl from normal myocardium beginning 10 min after 201Tl injection and increased extraction of 201Tl from the blood pool immediately after release of a transient occlusion. Redistribution of 201Tl therefore begins very soon after relief of myocardial ischemia and even a short delay in initiating myocardial imaging may decrease the sensitivity of the technique for detecting transient ischemia.     

Exercise-induced ischemia initiates the second window of protection in humans independent of collateral recruitment

OBJECTIVES: This study was designed to examine if exercise-induced ischemia initiated late preconditioning in humans that becomes manifest during subsequent exercise and serial balloon occlusion of the left anterior descending coronary artery (LAD). BACKGROUND: The existence of late preconditioning in humans is controversial. We therefore compared myocardial responses to exercise-induced and intracoronary balloon inflation-induced ischemia in two groups of patients subjected to different temporal patterns of ischemia. METHODS: Thirty patients with stable angina secondary to single-vessel LAD disease underwent percutaneous coronary intervention (PCI) after two separate exercise tolerance test (ETT) protocols designed to investigate isolated early preconditioning (IEP) alone or the second window of protection (SWOP). The IEP subjects underwent three sequential ETTs at least two weeks before PCI. The SWOP subjects underwent five sequential ETTs commencing 24 h before PCI. RESULTS: During PCI there was no significant difference in intracoronary pressure-derived collateral flow index (CFI) between groups (IEP = 0.15 +/- 0.13, SWOP = 0.19 +/- 0.15). In SWOP patients, compared with the initial ETT, the ETT performed 24 h later had a 40% (p < 0.001) increase in time to 0.1-mV ST depression and a 60% (p < 0.05) decrease in ventricular ectopic frequency. During the first balloon inflation, peak ST elevation was reduced by 49% (p < 0.05) in the SWOP versus the IEP group, and the dependence on CFI observed in the IEP group was abolished (analysis of covariance, p < 0.05). The significant attenuation of ST elevation (47%, p < 0.005) seen at the time of the second inflation in the IEP patients was not seen in the SWOP patients. CONCLUSIONS: Exercise-induced ischemia triggers late preconditioning in humans, which becomes manifest during exercise and PCI. This is the first evidence that ischemia induced by coronary occlusion is attenuated in humans by a late preconditioning effect induced by exercise.     

Detection of myocardial ischemia in the elderly versus the young by stress thallium-201 scintigraphy and its relation to important coronary artery disease

The prevalence and severity of coronary atherosclerosis increase dramatically with age, so that more than half of all deaths in persons aged over 65 are due to coronary arterial disease (CAD) and about three fourths of all deaths from CAD occur in the elderly. The aims of our study were, first, to detect myocardial ischemia development in elderly versus younger patients undergoing treatment for known CAD through the use of both conventional treadmill testing and ²⁰¹Tl scintigraphy, and second, to determine the relationship between the above non-invasive tests and angiographically confirmed important coronary artery disease (iCAD). A database of 606 patients (355 men and 251 women) who had undergone coronary angiography, exercise ECG testing (ETT) using the treadmill Bruce protocol, and ²⁰¹Tl scintigraphy, was reviewed retrospectively. All patients had displayed clinical expression of CAD with or without the existence of an old myocardial infarction (MI). The patients were from both sexes (440 men and 252 women) and divided into two groups, according to age. Group A was composed of 265 patients aged over 65 (170 men, 95 women, mean age = 70.3 ± 5.3 years). Group B was composed of 341 patients aged under 65 (185 men, 156 women, mean age 54.4 ± 9.1 years). Patients with uncontrolled arterial hypertension, hypertrophic cardiomyopathy, severe valve diseases, severe chronic obstructive lung diseases, severe anemia, peripheral atherosclerosis, orthopedic problems, or Parkinson's disease were excluded from the study. The term "important coronary artery disease" (iCAD) covers the following patterns of coronary anatomy: (a) left main stem stenosis ≥50% with or without disease elsewhere, (b) proximal three-vessel disease, (c) three-vessel disease including the proximal left anterior descending artery (LAD), (d) proximal two-vessel disease including LAD, and (e) two-vessel disease including the proximal LAD. Biostatistical characteristics such as sensitivity, specificity, and predictive values of ETT-²⁰¹Tl were estimated. Analyzing our results we concluded that: the biostatistical parameters in predicting important CAD in elderly and younger patients by means of exercise test and thallium scintigraphy need to be redefined through more closely scheduled and prospective studies; in elderly coronary patients, the appearance of positive results in both parameters of ETT-²⁰¹Tl indicates a significant possibility of iCAD existence; in coronary patients younger than 65 years, the appearance of negative results in both parameters of ETT-²⁰¹Tl almost excludes iCAD, in contrast to elderly patients, who display a significant proportion of iCAD; in elderly coronary patients, the appearance of equivocal results in both tests indicates a significant possibility of the existence of iCAD, in contrast to younger patients. Received: October 15, 2001 / Accepted: January 12, 2002     

Exercise-induced left bundle branch block during thallium 201 myocardial perfusion scintigraphy--a case report

Exercise-induced left bundle branch block (Ex-LBBB) is a rare entity encountered during exercise testing. The authors present a 53-year-old woman who developed intermittent Ex-LBBB asymptomatically during Tl 201 myocardial perfusion scintigraphy. Scintigraphic findings revealed septal-anteroseptal ischemia while the coronary arteriogram appeared normal. False-positive septal-anteroseptal scintigraphic findings suggesting ischemia in patients with persistent left bundle branch block (LBBB) is well known, but since the LBBB in this case was induced by exercise testing and was spontaneously terminated at rest, scintigraphic findings may be attributed to microcirculatory ischemia, which cannot be detected angiographically, as the cause of Ex-LBBB.     

Exercise performance-based outcomes of medically treated patients with coronary artery disease and profound ST segment depression

OBJECTIVES

We sought to determine the relationship between exercise duration and cardiovascular outcomes in patients with profound (≥2 mm) ST segment depression during exercise treadmill testing (ETT).

BACKGROUND

Patients with stable symptoms but profound ST segment depression during ETT are often referred for a coronary intervention on the basis that presumed severe coronary artery disease (CAD) will lead to unfavorable cardiovascular outcomes, irrespective of symptomatic and functional status. We hypothesized that good exercise tolerance in such patients treated medically is associated with favorable long-term outcomes.

METHODS

We prospectively followed 203 consecutive patients (181 men; mean age 73 years) with known stable CAD and ≥2 mm ST segment depression who are performing ETT according to the Bruce protocol for an average of 41 months. The primary end point was occurrence of myocardial infarction (MI) or death.

RESULTS

Eight (20%) of 40 patients with an initial ETT exercise duration ≤6 min developed MI or died, as compared with five (6%) of 84 patients who exercised between 6 and 9 min and three (3.8%) of 79 patients who exercised ≥9 min (p = 0.01). Compared with patients who exercised ≤6 min, increased ETT duration was significantly associated with a reduced risk of MI/death (6 to 9 min: relative risk [RR] = 0.25, 95% confidence interval [CI] 0.08 to 0.76; >9 min: RR = 0.14, 95% CI 0.04 to 0.53). This protective effect persisted after adjustment for potentially confounding variables. We observed a 23% reduction in MI/death for each additional minute of exercise the patient was able to complete during the index ETT.

CONCLUSIONS

Optimal medical management in stable patients with CAD with profound exercise-induced ST segment depression but good ETT duration is an appropriate alternative to coronary revascularization and is associated with low rates of MI and death.     

Bundle branch blocks and/or hemiblocks complicating acute myocardial ischemia or infarction

Despite the bulk of anatomical and histologic evidence supporting the existence of three fascicules in the left branch of the His bundle, the concept of a bifascicular system proposed by Rosenbaum and his school has been adopted by the cardiological community as a practical teaching tool. Left anterior hemiblock (LAH) refers to block of the antero-superior branch of the left branch which is small and left posterior hemiblock (LPH) to block of the postero-inferior branch which is larger. The LAH is more common that the LPH and often associated with a complete right bundle branch block (RBBB). Coronary artery disease (CAD) is a major cause of hemiblocks. In this review article, we discuss various aspects of the relation of hemiblocks with CAD. We looked at the prevalence of LAH in consecutive patients undergoing coronary angiography and who had a significant coronary lesion in one vessel or more. In all patients with LAH, a significant lesion of the left anterior descending coronary artery was present, with in the majority of patients, an impairment of the left ventricular function. Bifascicular block (RBBB with LAH or LPH) can complicate acute myocardial infarction and is often associated with a poor prognosis and the presence of heart failure. Thrombolysis and or early angioplasty in acute myocardial infarction have significantly improved the prognosis and reduced the mortality associated with bifascicular block. Left anterior hemiblock pattern was also observed during angina pectoris occurring at rest or induced by exercise or atrial pacing. In these circumstances, LAH is transient and is likely to be due to ischemia in the anterolateral wall related to a lesion of the main trunk or the proximal left anterior descending coronary artery with the postero-inferior wall being first depolarized. The presence of bifascicular block in acute myocardial infarction still is associated with an unfavorable prognosis as compared to non-bundle branch block patients because of the common association with heart failure and other comorbidities.     

Myocardial metabolic, hemodynamic, and electrocardiographic significance of reversible thallium-201 abnormalities in hypertrophic cardiomyopathy

BACKGROUND. Exercise-induced abnormalities during thallium-201 scintigraphy that normalize at rest frequently occur in patients with hypertrophic cardiomyopathy. However, it is not known whether these abnormalities are indicative of myocardial ischemia. METHODS AND RESULTS. Fifty patients with hypertrophic cardiomyopathy underwent exercise 201Tl scintigraphy and, during the same week, measurement of myocardial lactate metabolism and hemodynamics during pacing stress. Thirty-seven patients (74%) had one or more 201Tl abnormalities that completely normalized after 3 hours of rest; 26 had regional myocardial 201Tl defects, and 26 had apparent left ventricular cavity dilatation with exercise, with 15 having coexistence of these abnormal findings. Of the 37 patients with reversible 201Tl abnormalities, 27 (73%) had metabolic evidence of myocardial ischemia during rapid atrial pacing (myocardial lactate extraction of 0 mmol/l or less) compared with four of 13 patients (31%) with normal 201Tl scans (p less than 0.01). Eleven patients had apparent cavity dilatation as their only 201Tl abnormality; their mean postpacing left ventricular end-diastolic pressure was significantly higher than that of the 13 patients with normal 201Tl studies (33 +/- 5 versus 21 +/- 10 mm Hg, p less than 0.001). There was no correlation between the angiographic presence of systolic septal or epicardial coronary arterial compression and the presence or distribution of 201Tl abnormalities. Patients with ischemic ST segment responses to exercise had an 80% prevalence rate of reversible 201Tl abnormalities and a 70% prevalence rate of pacing-induced ischemia. However, 69% of patients with nonischemic ST segment responses had reversible 201Tl abnormalities, and 55% had pacing-induced ischemia. CONCLUSIONS. Reversible 201Tl abnormalities during exercise stress are markers of myocardial ischemia in hypertrophic cardiomyopathy and most likely identify relatively underperfused myocardium. In contrast, ST segment changes with exercise and systolic compression of coronary arteries on angiography are unreliable markers of inducible myocardial ischemia in hypertrophic cardiomyopathy. Apparent cavity dilatation during 201Tl scintigraphy may indicate ischemia-related changes in left ventricular filling, with elevation in diastolic pressures and endocardial compression.     

Abnormal heart rate recovery after exercise: a comparison with known indicators of increased mortality.

BACKGROUND: Abnormal heart rate (HR) recovery at 1 min after exercise (< or =12 beats) was recently suggested to be a predictor of all cause and cardiac mortality. AIM: This study aimed to (1) correlate HR recovery at 1 min after exercise with known exercise and myocardial perfusion markers of increased cardiac mortality, and (2) compare the known exercise and myocardial perfusion markers of increased cardiac mortality between patients with a normal and abnormal HR recovery at 1 min after exercise. METHODS: One hundred patients with known or suspected coronary artery disease referred for exercise stress testing (ETT) were prospectively enrolled. Percent, ETT time peak HR, HR reserve, summed stress score (SSS), extent of stress (SE%) and reversible perfusion abnormalities (RE%) were recorded in every patient. RESULTS: There was poor correlation with markers of myocardial ischemia or infarction [SSS (r = 0.15), SE% (r = 0.05), RE% (r = 0.12), all p = n.s.] but highly significant correlation between HR recovery at 1 min after exercise and chronotropic variables [ETT time (r = 0.56), peak HR (r = 0.65), HR reserve % (r = 0.64), all p < 0.001]. Patients on beta-blockers had significantly more incidence of an abnormal HR recovery at 1 min after exercise, compared to patients not on beta-blockers (88 vs. 56%, p < 0.01). CONCLUSION: Abnormal HR recovery at 1 min after exercise has no correlation with known myocardial perfusion markers of increased cardiac mortality. Patients with an abnormal HR recovery do not appear to have an increased incidence or more severe myocardial infarction or ischemia. However, there is a strong correlation between HR recovery at 1 min after exercise and the chronotropic variables during exercise.     

Angiographic localization of potential culprit coronary arteries in patients with interatrial block following a positive exercise tolerance test

Interatrial block (IAB), denoted by P waves > or =110 ms, is believed to be associated with underlying ischemia, particularly with that of its principal interatrial conduction pathway, the Bachmann bundle. We investigated if there is an angiographic association of IAB on electrocardiograms at rest in patients who underwent cardiac angiography after a positive exercise tolerance test (ETT) result. Twenty-seven patients with IAB and 42 control patients without IAB on electrocardiograms at rest who had evidence of ischemia on cardiac angiography after ETT were identified. Coronary vessels that were angiographically most significantly stenosed (> or =70% occlusion indicating stenosis) were noted for statistical comparison (a p value <0.05 was considered statistically significant). Among patients with IAB, the right coronary artery was the predominant vessel to be affected, with > or =70% narrowing compared with the left, inclusive of the left main, left circumflex, obtuse marginal, and diagonal coronary arteries (58% vs 23%, p = 0.03). Right coronary artery lesions in patients with IAB were mostly in the proximal and mid portions (54% vs 25% for the entire left coronary artery, p = 0.02). No such difference was noted in control subjects. In conclusion, in patients with IAB at rest who have coronary heart disease, the right coronary artery is predominantly more significantly affected.