Effect of coronary artery disease and myocardial ischaemia on transmyocardial platelet aggregability

Twenty-five patients with coronary artery disease and six ‘normal’subjects were studied during routine catheter investigationfor chest pain. In vitro platelet aggregation responses weremeasured in arterial and coronary sinus blood samples takenat rest and after pacing. Platelet aggregability was found tobe increased in coronary sinus blood from patients with coronaryartery disease at rest, but it was reduced with pacing. We concludethat platelets are affected by passage through a stenosed coronaryartery and that acute myocardial ischaemia exerts an anti-aggregatoryeffect.     

Prognostic value of thallium-201 myocardial scintigraphy after atrial transoesophageal pacing in patients with suspected coronary artery disease

Fifty-five patients with suspected coronary artery disease underwentplanar thallium-201 myocardial scintigraphy after atrial transoesophagealpacing. Coronary angiography was carried out in all patients.Eighteen patients had no myocardial infarction, but a greaterthan 50% narrowing of at least one main vessel: initial hypoperfusionwith redistribution at 4 h occurred in 16 patients (sensitivity89%). Twenty-one patients had had a previous myocardial infarction:a reversible thallium defect was observed in 12 patients andan irreversible defect in the nine remaining patients. Sixteenpatients had normal coronary arteries: a reversible thalliumdefect was observed in three patients (specflcity 81%). Aftera mean follow-up of 22±13 months (range 6 to 40), 23cardiac events occurred: cardiac death in one patient, unstableangina in three, and revascularization procedures for recurrentangina despite medical therapy in 19 (coronary artery bypasssurgery in 7 and coronary angioplasty in 12). By univariateanalysis, the predictors of future cardiac events were a historyof previous myocardial infarction (odds ratio 55, P<0.02)multivessel coronary artery disease (odds ratio 9.6, P<0.0002),angina during atrial pacing (odds ratio 5.1, P<0.05), abnormalscintigraphy (odds ratio 17.1, P<0.001) and reversible perfusiondefect after pacing (odds ratio 7.9, P<0.002). By multivariateanalysis, multivessel disease (P<0.004) and reversible perfusiondefect after pacing (P<0.02) were the only independent predictorsof future cardiac events. In conclusion, thallium-201 myocardial scintigraphy after transoesophagealatrial pacing is accurate for the diagnosis and prognosis ofpatients with suspected coronary artery disease, and may beundertaken in patients unable to perform exercise stress testing.     

Radionuclide left ventricular function curve during atrial pacing in normal subjects and in patients with coronary artery disease

We used radionuclide angiography during right atrial pacing to assess left ventricular function in 7 normal subjects and 20 patients with coronary artery disease. A left ventricular function curve relating stroke volume to end-diastolic volume was plotted for each patient. The normal pacing ventricular function curve was a straight line passing through the origin of axes. The pacing ventricular function curve was abnormal in 18 of the 20 patients with coronary artery disease, and three different shaped curves were obtained, reflecting decreased contractile force for the same end-diastolic volume during ischemia. Cardiac output and blood pressure do not change during atrial pacing, thus the Frank-Starling relationship is evaluated by this method during almost experimentally controlled conditions. Relating stroke volume to end-diastolic volume, and not end-diastolic pressure, distinguishes between overall left ventricular systolic function and left ventricular compliance.     

无创血流储备分数测定对冠心病患者心肌缺血功能评估的临床进展

在中度病变的稳定型冠状动脉疾病(CAD)患者中,判断病变是否造成了冠状动脉远端血流动力学的显著改变(即心肌缺血),在制定临床决策中起着至关重要的作用。而在这些临界病变中,血流储备分数(FFR)测定是识别心肌缺血存在与否的金标准。近年来,随着计算机流体动力学(CFD)的发展,基于冠状动脉CT血管造影的无创性FFR(FFRCT)得以发展。本综述旨在通过阐述FFRCT的概念及应用原理,总结目前针对FFRCT技术的几项临床研究,说明其良好的诊断性能、临床实践进展、优点、局限性以及临床应用前景。     

Association between plasma homocysteine and myocardial SPECT abnormalities in patients referred for suspected myocardial ischaemia

Background

Elevated plasma homocysteine level has emerged as a relatively newly recognised risk factor for coronary artery disease (CAD). However, reduction of plasma homocysteine levels in large prospective studies did not appear to reduce the risk for subsequent cardiac events. In this study, we investigated the association between plasma homocysteine levels and quantitative indices of myocardial perfusion SPECT imaging in patients referred for myocardial ischaemia.

Methods

Quantitative myocardial perfusion SPECT indices were obtained for 120 patients who were recruited for the study. All patients underwent a two-day rest–stress myocardial perfusion imaging. Plasma venous sampling was done on all patients after an overnight fast. Of the 120 participants (mean age 56 years, 53% males), 33% had elevated plasma homocysteine levels. The plasma homocysteine level was then compared to the results of imaging and other known risk factors.

Results

After adjustment for traditional risk factors of coronary artery disease, patients with elevated homocysteine levels had a significantly higher mean summed stress score (SSS) (11.3 vs 6.9, p = 0.02) than patients with a normal homocysteine level. This was true for both single- and multivessel disease. Also, patients with elevated homocysteine levels had a higher stress end-systolic volume (SESV) (137 vs 105 ml, p = 0.03) and lower post-stress left ventricular ejection fraction (SEF) (54 vs 64%, p = 0.02). The patients with elevated plasma homocysteine levels also had a significantly lower mean body mass index (BMI) (26.6 vs 30.6 kg/m², p = 0.002). There was a significant relationship between the total number of known risk factors in a patient with CAD and the proportion of patients presenting with elevated plasma homocysteine levels (p = 0.03). Also, the extent of infarct, as measured by the summed rest score (SRS), was more closely correlated with an elevated homocysteine level than with the degree of ischaemia.

Conclusion

There was a correlation between plasma homocysteine level and the presence and extent of myocardial perfusion abnormalities in patients with established coronary artery disease, in particular those with multiple risk factors and multi-vessel infarction.     

Evaluation of potential adverse effects of sodium nitroprusside during pacing-induced myocardial ischaemia in man

To elucidate the potential harmful effects of sodium nitroprusside(NP) on myocardial ischaemia, eleven patients with coronaryartery disease were studied before and during two doses NP infusion.The infusion rates were adjusted to reduce systolic aortic pressureby 10–20 mmHg and to between 100 and 110 mmHg. Myocardialhaemodynamic and metabolic measurements were undertaken in sinusrhythm and during pacing-induced angina pectoris. The procedurewas repeated at the low and high dose NP using the same pacingrate. One patient did not develop ischaemia and was excluded.Low dose NP reduced ischaemia slightly, whereas the higher dosehad no effect despite falling indices of cardiac work. The oxygenuptake was maintained except at high dose treatment during pacingdue to an increased catecholamine stimulation. The transmuralperfusion gradient was unchanged at low dose NP, but fell atthe higher dose suggesting reduced perfusion of ischaemic tissue.High dose NP also decreased coronary arteriolar resistance considerablywhich may have induced a coronary ‘steal’ effect.Thus, NP may induce adverse haemodynamic and metabolic changeswhich counteract the beneficial actions of the drug on ischaemiawhen used in high doses and in patients without heart failure.     

Characterization and long-term prognosis of patients with effort-induced silent myocardial ischaemia.

The aim of this study was to evaluate the anatomo-clinical correlations and the prognostic significance of silent myocardial ischaemia (SI) during exercise testing (ET). Four hundred and six patients with angiographically proven CAD and positive ET were studied. Patients were divided into two groups: 309 patients (Group A) with positive ET for both electrocardiographical findings and angina, and 97 patients (Group B) with positive ET for electrocardiographical findings but not for angina (SI). In Group A the following clinical characteristics differed significantly from Group B: incidence of diabetes mellitus (15.8% vs 27.8%, P less than 0.04); duration of disease (less than 1 month from its first manifestation) (30.4% vs 54.6%, P less than 0.001) and a positive ET at low work-load (41.7% vs 50.5%, P less than 0.05). Mortality during follow-up (mean 72 +/- 11 months) was 8.6% in Group A and 8.2% in Group B (NS). Incidence of sudden death was similar in the two groups (2.9% vs 2.06%; NS). The multivariate analysis shown as independent variables, related significantly with a poor prognosis in both groups: left ventricular function (P less than 0.0001); prior myocardial infarction (P less than 0.0001); and multivessel disease (P less than 0.001). In conclusion, patients with a recent onset of symptoms, a positive ET at low workload and diabetes mellitus are more likely to present SI during ET. The long-term prognosis and the incidence of sudden death are similar in patients with painful and painless myocardial ischaemia during ET.     

A warm footbath improves coronary flow reserve in patients with mild-to-moderate coronary artery disease

Backgrounds: Recent studies have shown that thermal therapy by means of warm waterbaths and sauna has beneficial effects in chronic heart failure. However, a comprehensive investigation of the hemodynamic effects of thermal vasodilation on coronary arteries has not been previously undertaken. In this study, we studied the effect of a warm footbath (WFB) on coronary arteries in patients with coronary artery disease (CAD), as well as any adverse effect. Methods: We studied 21 patients (33.3% men, mean age 60.8 ± 13.5 years) with CAD. Coronary flow Doppler examination of the left anterior descending coronary artery and coronary flow reserve (CFR) were performed and measured using adenosine before and after a WFB. Results: Systolic and diastolic blood pressure and heart rate did not change with the WFB. Mean velocity of diastolic coronary flow significantly increased (diastolic mean flow velocity: 18.3 ± 7.1 cm/sec initial, 21.5 ± 8.0 cm/sec follow‐up, P = 0.002) and CFR significantly improved (1.6 ± 0.4 vs. 2.2 ± 0.5, P < 0.001) after WFB. The WFB was well accepted and no relevant adverse effects were observed. The change of CFR after WFB correlated well with diastolic function (E’, r = 0.51, P = 0.031; E/E’, r =–0.675, P = 0.002). Conclusions: A WFB significantly improved CFR without any adverse effects in patients with mild‐to‐moderate CAD and can be applied with little risk of a coronary artery event if appropriately performed. (Echocardiography 2011;28:1119‐1124)     

Left ventricular response to exercise in coronary artery disease: relation to myocardial ischaemia and effects of nifedipine

To assess the relationship between left ventricular (LV) responseto exercise and myocardial ischaemia, 40 patients with coronaryartery disease (CAD) and 17 control subjects underwent radionuclideventriculo-graphy at rest and during semiupright exercise. In14 of the 40 patients with CAD, radionuclide exercise studieswere repeated 20 min after 20 mg of sublingual nifedipine. Patientswith CAD had increases in both LV end-diastolic and end-systolicvolumes and no change in ejection fraction during exercise.End-systolic volume increased and ejection fraction decreasedsignificantly more in patients with multivessel disease, exercise-inducedangina and/or ischaemic ST segment depression. Nifedipine reducedangina and ST-segment depression during exercise, attenuatedexercise-induced increase in end-diastolic and end-systolicvolumes and improved eject ion fraction. This study suggests that in patients with CAD, the responseof LV volumes and ejection fraction to exercise is related tothe degree of exercise-induced myocardial ischaemia and nifedipineimproves exercise LV performance     

Doppler echocardiography during transesophageal atrial pacing in the detection of coronary artery disease Stress Doppler echocardiography in the detection of coronary artery disease

The aim of this study was to assess the applicability of the Doppler echocardiogram (EchoKG) during transesophageal atrial pacing (TAP) with respect to the detection of coronary artery disease (CAD). Aortic flow peak velocity (PV), mean acceleration (MA), stroke distance (SD), minute distance (MD) and time to PV were measured using pulsed Doppler EchoKG during sinus rhythm and at pacing rates of 120 and 140 bpm in 11 patients, taken as subjects, with CAD defined by coronary arteriography and 15 patients without CAD (the control group). Similar changes of PV, SD, MD and time to PV during TAP were observed in subjects with and without CAD. Only changes of MA were different between subjects with and without CAD:MA during TAP remained unchanged in the control group and decreased from 1055.2±49.7 cm/s² (baseline) to 829.0±55.9 cm/s² at a pacing rate 140 bpm (p<0.05) in subjects with CAD. On the basis of these data we suggest a new criterion for the detection of hemodynamically significant CAD: decrease of MA at a pacing rate of 140 bpm>15% of initial value. Its specificity and sensitivity in the detection of CAD were respectively 87% and 82%.We conclude that the Doppler EchoKG during TAP is a relatively simple and reliable method for the diagnosis of CAD, and that the response of the Doppler EchoKG parameter of MA to TAP is a sensitive and specific index, useful for the detection of significant coronary artery stenosis.     

Comparative effects of intravenous dipyridamole and sublingual nitroglycerin on coronary hemodynamics and myocardial metabolism at rest and during atrial pacing in patients with coronary artery disease

The effects of intravenous dipyridamole (20 mg) and sublingual nitroglycerin (0.6 mg) were compared at rest and during rapid atrial pacing in patients with significant coronary obstruction. Dipyridamole, which had no significant effect on resting systolic blood pressure, caused a significant increase in coronary sinus flow (CSF) and reduction of coronary vascular resistance (CVR) and arterial-coronary sinus oxygen difference (AO₂-CSO₂δ), whereas nitroglycerin reduced resting systolic pressure but had no significant effect on CSF, CVR, or AO₂-CSO₂°. Although these effects of dipyridamole and nitroglycerin on resting systolic pressure, CSF, CVR, and AO₂-CSO₂° were qualitatively similar during rapid atrial pacing, the onset of chest pain and ischemic ECG changes occurred at a lower heart rate following dipyridamole (136±5 beats/min) than following nitroglycerin (149±6 beats/min, p<0.01). However, maximal double product and myocardial oxygen consumption achieved during pacing were similar following both dipyridamole and nitroglycerin and were less than control pacing values. Coronary dilatation following dipyridamole appears to reduce tolerance to pacing-induced ischemia probably by maldistribution of coronary flow away from ischemic myocardium. Nitroglycerin differs from dipyridamole by improving tolerance to pacing; however, this difference appears to be due to systemic vasodilator effects of nitroglycerin rather than to enhancement of flow to ischemic myocardium.     

Release of atrial natriuretic peptide in relation to metabolic changes during myocardial ischaemia induced by coronary angioplasty

The inter-relationships between ischaemia-induced metabolicchanges and atrial natriuretic peptide (ANP) release were studiedin 18 patients undergoing elective percutaneous transluminalcoronary angioplasty (PTC A). Transcardiac differences in ANP,lactate, pH, pCO₂ and O₂ saturation were analysed before andafter balloon inflation. The patients were divided into ischaemiaand non-ischaemia groups on the basis of the change in lactateextraction ratio during balloon inflation. The ischaemia group(patients with a decrease in lactate extraction ratio) showedan increase of 27±15 pg. ml^–1 in the transcardiacANP difference, whereas a decrease of 27±17pg.ml^–1occurred in the non-ischaemia group (no decrease in lactateextraction ratio). The change between the two patient groupswas statistically significant (P<0.05). Metabolic ‘pre-conditioning’was not observed in patients with successive dilatations, thereforedata from all the dilatations were combined and evaluated byregression analysis. A correlation coefficient of 0.40 (P<0.05)was obtained between the PTCA-induced changes in transcardiacANP and lactate differences. We conclude that transient myocardialischaemia induced by PTCA increases circulating ANP concentrationsin patients with signs of metabolic ischaemia, but not in thosewithout.     

Effectiveness of triple-site triggered atrial pacing for prevention of atrial fibrillation after coronary artery bypass graft surgery

BACKGROUND: Recently, several temporary multisite pacing methods have been developed for prevention of postoperative atrial fibrillation (AF). HYPOTHESIS: In this study, we evaluated the effect of triple-site temporary triggered pacing in the AAT mode on the development of AF in patients undergoing coronary artery bypass graft (CABG) at high risk for developing postoperative AF. METHODS: A total of 70 patients undergoing CABG were randomly assigned either to pacing group (study group, n = 35 patients) or to no pacing group (control group, n = 35 patients). The external pacemaker was programmed to pace at the atrial triggered mode at a lower rate of 40 beats/min for 4 days. RESULTS: Atrial fibrillation, defined as lasting > 30 s, occurred in 4 patients (11.4%) in the study group and in 16 patients (45.7%) in the control group (p = 0.003). Sustained AF, defined as AF lasting > 10 min, also was observed less frequently in the study group than in the control group (11.6 vs. 37.1%, p = 0.024). Triple-site triggered atrial pacing was observed to reduce the incidence of AF by 75% and the incidence of sustained AF by 69%. CONCLUSIONS: We believe that multiple-site temporary pacing in the triggered mode is an effective way of preventing postoperative AF. This technique may be used especially in patients at high risk of developing AF.     

Nocturnal myocardial ischemic events and sleep-disordered breathing in patients with coronary artery disease

Objective To investigate the occurrence of nocturnal myocardial ischemia and its relationship with sleep-disordered breathing(apneas and oxygen desaturations)in patients with angina pectoris undergoing coronary an-giography.Methods Eighty-two men and 14 women referred for consideration of coronary intervention wererandomly selected.Observation by an overnight sleep monitor and Holter recording were performed to studysleep-disordered breathing(oxyhemoglobin desaturations≥4% and apnea-hypopneas),heart rates,and ST-seg-ment depressions(≥1mm,≥1 min).Results Nocturnal ST-segment depressions occurred in 37% of thepatients.ST-segment depression within 2 min after an apnea-hypopnea or desaturation occurred in 17% of thepatients.This temporal association was seen in 21% of the patients with nocturnal ST-segment depressions,morefrequendy in men(P<0.05)and more frequently in those with severe disordered breathing(P<0.05).Mostof these ST-segment depressions were preceded by a series of breathing events:repeated apnea-hypopneas or de-saturations or both in 73% of the patients.Conclusions Episodes of nocturnal myocardial ischemia are com-mon in patients with angina pectoris.A temporal relationship between sleep-disordered breathing and myocardialischemia was present in some of our patients,and occurs more frequently in men and in those with severely dis-ordered breathing.(J Geriatr Cardiol 2004;1(2):90-94.)     

Exercise-induced myocardial ischaemia detected by cardiopulmonary exercise testing.

BACKGROUND: The objective of the study was to identify the parameter(s) of cardiopulmonary exercise testing (CPET) that can detect exercise-induced myocardial ischaemia (EIMI), and to determine its diagnostic accuracy for identifying patients with coronary artery disease (CAD). METHODS AND RESULTS: We prospectively studied 202 consecutive patients (173 men, 29 women, mean age 55.7+/-10.8 years) with documented CAD. All patients underwent an incremental exercise stress testing (ECG-St) with breath-by-breath gas exchange analysis, followed by a 2-day stress/rest gated SPECT myocardial scintigraphy (GSMS) as the gold standard for ischaemia detection. ROC analysis selected a two-variable model-O(2)pulse flattening duration, calculated from the onset of myocardial ischaemia to peak exercise, and deltaVO(2)/deltawork rate slope-to predict EIMI by CPET. GSMS identified 140 patients with reversible myocardial defects, with a Summed Difference Score (SDS) of 9.7+/-2.8, and excluded EIMI in 62 (SDS 1.3+/-1.6). ECG-St had low sensitivity (46%) and specificity (66%) to diagnose EIMI as compared with CPET (87% and 74%, respectively). CONCLUSIONS: The addition of gas exchange analysis improves the diagnostic accuracy of standard ECG stress testing in identifying EIMI. A two-variable model based on O(2)pulse flattening duration and deltaVO(2)/deltawork rate slope had the highest predictive ability to identify EIMI.     

Detection of impaired coronary flow reserve in coronary artery disease using transthoracic echocardiographic assessment of coronary sinus blood flow

In order to establish whether coronary flow reserve (CFR) can be measured by transthoracic echocardiography (TTE) with pulse wave Doppler echocardiography, 14 patients with coronary artery disease (CAD) and 12 normal subjects were studied. Coronary sinus blood flow was measured at rest and 2 minutes after intravenous injection of 0.56 mg/kg dipyridamole (DP). CFR was calculated as the DP to rest flow ratio. Patients with CAD were found to have significantly decreased CFR when compared to normal subjects. These findings suggest that TTE may be useful in diagnosing CAD.     

The adequacy of myocardial revascularization in patients with multivessel coronary artery disease

In patients with multi-vessel coronary artery disease (MVCAD) myocardial revascularization may be accomplished either on all diseased lesions – complete myocardial revascularization – or on selectively targeted coronary segments by percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). Complete revascularization has a potential long-term prognostic benefit, but is more complex and may increase in-hospital events when compared with incomplete revascularization.