DPTI/STTI—An index of the myocardial oxygen supply/demand ratio?

The DPTI/STTI (diastolic pressure-time index/tension-time index) ratio is applied as an indicator of myocardial ischemia particularly in cardiovascular and anesthesiologic care units. The validity of the DPTI/STTI ratio was examined in intact dogs with large variations of oxygen supply and demand. The correlation of DPTI/STTI to the directly measured oxygen supply/demand ratio was poor even under maximal coronary vasodilatation. Many data points were far below the critical DPTI/STTI values (reported previously) without occurrence of myocardial ischemia, failure, or edema. Therefore caution is necessary if the DPTI/STTI ratio is to be applied to humans.     

Effects of propranolol on coronary hemodynamic and metabolic responses to tachycardia stress in patients with and without coronary disease

To clarify the influence of propranolol—and particularly its heart-rate effects—on myocardial ischemia, coronary hemodynamics and metabolism were studied in 15 patients utilizing a protocol to control heart rate. Ten patients had significant coronary narrowing (CAD) and 5 were normal. Systemic pressure, coronary sinus blood flow (CSBF), left ventricular oxygen utilization (LVV?O₂), ST Segment depression, and myocardial lactate extraction were measured before and after propranolol (10 mg IV), at rest, and during pacing-induced tachycardia stress. Propranolol-related reduction in CSBF and LVV?O₂ at rest was reversed when heart rate was controlled in both patient groups. Propranolol failed to alter heart-rate threshold, tension-time index (TTI), CSBF, or LVV?O₂ at angina in the CAD patients. Likewise, ischemic-type ST depression, decreases in lactate extraction, and coronary resistance were unchanged compared to values observed during tachycardia stress before propranolol. In normal coronary patients, propranolol also produced no significant change in LVV?O₂ or coronary resistance when its heart rate effects were controlled. These data imply that a major coronary and metabolic influence of propranolol relates to changes occurring secondary to its influence on heart rate. Furthermore, this agent's anti-ischemic effect is not prominent during tachycardia stress suggesting that this stress test may be clinically useful in patients taking propranolol.     

Effect of myocardial oxygen consumption on infarct size in experimental coronary artery occlusion

Summary The influence of myocardial oxygen consumption (MVO₂) at the moment of coronary occlusion on the size of the ensuing necrosis was investigated in 12 anaesthetised dogs. A two-infarction model was used with a sequential occlusion of two distant coronary branches in the same heart, however under different levels of MVO₂. One group of occlusions was produced at a high MVO₂ of 21.6±3.0 ml O₂... min^–1. 100 g^–1. This group was compared with a second in which necrosis proceeded at a low MVO₂ estimated to be 5.9±1.5 ml O₂·min^–1. 100 g^–1 averaged over a 90-min occlusion period. Infarct size expressed as percentage of perfusion area was 43±28% in group 1 and 11±11% in group 2 (p<0.005). The mass of the perfusion area was equal in both groups (17±4 g, 19±6 g). The amount of myocardial necrosis, which after a 90-min occlusion depends on the acute collateral blood flow, was in every case greater under high MVO₂. Thus a low MVO₂ at the moment of occlusion can postpone myocardial necrosis.

---

Zusammenfassung Der Einfluß des kardialen Sauerstoffverbrauchs (MVO₂) auf die Infarktgröße wurde bei 12 narkotisierten Hunden untersucht. Zwei voneinander völlig getrennte Seitenäste der linken Koronararterie wurde nacheinander am selben Herzen verschlossen. Das erste Gefäßkollektiv wurde bei einem MVO₂ von 21,6±3,0 ml ·min^–1. 100 g^–1 okkuldiert, das zweite bei einem MVO₂ von 5,9±1,5ml·min^–1 ·100g^–1. Die Infarktgröße, ausgedrückt als Fraktion des Perfusionsgebietes, war 43±28% in Gruppe 1 und 11±11% in Gruppe 2 (p<0,005). Die Perfusionsgebiete, die okkludiert wurden, waren in beiden Gruppen gleich (17±4g, 19±6 g). Die Infarktgröße, die nach einer 90-min-Okklusion vom akuten Kollateralfluß abhängt, war in jedem Fall größer bei einem höheren MVO₂. Somit kann ein, niedrigerer MVO₂ zum Zeitpunkt des Verschlusses die Entwicklung der Nekrose zumindest hinauszögern.

     

The effect of diabetes on heart rate and other determinants of myocardial oxygen demand in acute coronary syndromes.

AIMS: To compare major determinants of myocardial oxygen demand (heart rate, blood pressure and rate pressure product) in patients with and without diabetes admitted with acute coronary syndromes. METHODS: A cross-sectional study of the relation between diabetes and haemodynamic indices of myocardial oxygen demand in 2542 patients with acute coronary syndromes, of whom 1041 (41.0%) had acute myocardial infarction and 1501 (59.0%) unstable angina. RESULTS: Of the 2542 patients, 701 (27.6%) had diabetes. Major haemodynamic determinants of myocardial oxygen demand were higher in patients with than without diabetes: heart rate 80.0 +/- 20.4 vs. 75.2 +/- 19.2 beats/minute (P < 0.0001); systolic blood pressure 147.3 +/- 30.3 vs. 143.2 +/- 28.5 mmHg (P = 0.002); rate-pressure product 11533 +/- 4198 vs. 10541 +/- 3689 beats/minute x mmHg (P < 0.0001). Multiple regression analysis confirmed diabetes as a significant determinant of presenting heart rate [multiplicative coefficient (MC) 1.05; 95% confidence interval (CI) 1.03-1.07; P < 0.0001], rate pressure product (MC 1.09; CI 1.05-1.12; P < 0.0001) and systolic blood pressure, which was estimated to be 3.9 mmHg higher than in patients without diabetes (P=0.003). These effects of diabetes were independent of a range of baseline variables including acute left ventricular failure and mode of presentation (unstable angina or myocardial infarction). CONCLUSIONS: In acute coronary syndromes, heart rate and other determinants of myocardial oxygen demand are higher in patients with than without diabetes, providing a potential contributory mechanism of exaggerated regional ischaemia in this high-risk group.     

Effects of transient increase in intrathoracic pressure on hemodynamic determinants of myocardial oxygen supply and demand

Effects of transient increases in intrathoracic pressure on hemodynamic indexes of myocardial oxygen supply and demand were evaluated in 21 patients with ischemic heart disease. Left ventricular, ascending aortic, and right atrial pressures and electrocardiogram (ECG) were recorded while a Valsalva maneuver was performed during ischemia. Myocardial oxygen demand was assessed from the tension time index (TTI) and cardiac size and potential myocardial oxygen supply were assessed from a diastolic pressure time index (DPTI) and relative changes in supply/demand ratio from DPTI/TTI. During an asymptomatic interval an abrupt but small transient decrease in TTI and cardiac size occurred during phase II (p less than 0.05) of the Valsalva maneuver. DPTI did not change significantly and DPTI/TTI increased (p less than 0.05). When Valsalva maneuver was initiated during angina, 16 patients reported prompt and complete relief of angina, and left ventricular end-diastolic pressure declined following the maneuver. Relief of ischemia occurred uniformly during the latter part of straining (phase II) coincident with the peak reduction in TTI, cardiac size, and increase in DPTI/TTI. These data indicate that a transient increase in intrathoracic pressure results in a decrease in hemodynamic determinants of myocardial oxygen demand and an increase in the myocardial oxygen supply:demand ratio.     

lschaemic heart disease: Endothelial dysfunction of the non-infarct related, angiographically normal, coronary artery in patients with an acute myocardial infarction

BACKGROUND: Patients with acute myocardial infarction and single-vesseldisease may have early atherosclerosis in other angiographicallynormal coronary arteries. METHODS: Coronary endothelial responses were analysed in 20 non-diabeticpatients with an acute myocardial infarction and one-vesseldiscase. In an angiographically normal, non-infarct related,coronary artery serial acetylcholine doses of 10^-6M, 10^-5M and10^-4M and nitroglycerin 40 µg were infused over 3 min.The responses of the coronary vessel were measured with quantitativeangiography. Coronary blood flow was also measured with a Dopplercatheter in ll of the 20 patients. RESULTS: Four patients showed a trend towards vasodilation during acetylcholineinfusion in the proximal and distal segments: from 2·49± 0·23 mm to 2·95 ± 0·42mm and 2·43 ± 0·56 mm to 2·81 ±0·66 mm, respectively. Coronary vascular resistance decreasedto 57 ± 4% (P=0·03). The other 16 patients presentedvasoconstriction in the proximal and distal segments: 2·61± 0·75 mm to 2·03 ± 0·65mm (P=0·0001), and 2·40 ± 0·58 to1·81 ± 0·56 mm (P=0·0036), respectively.Nitroglycerin caused vasodilation in the proximal (2·69± 0·61 mm, P=0·017, ANOVA) and distal segments(2·48 ± 0±45 mm, P=0·009, ANOVA).Coronary vascular resistance increased to 141 ± 43% (P=0·;03)over the basal value in this group of patients. CONCLUSION: Endothelial dysfunction of the epicardial and resistance vesselswas found in angiographically normal coronary arteries of patientswith one-vessel disease in 75% of this population.     

Left ventricular diastolic filling in patients with coronary artery disease without myocardial infarction

Left ventricular diastolic dysfunction at rest was studied in 24 patients with coronary artery disease but no evidence of previous myocardial infarction. Seven patients with normal coronary arteries were studied as control. Diastolic filling was analyzed by the serial left ventricular volume and 14 radial axes from the gravity point of the left ventricle with cine left ventriculography. There were no differences in the systolic function between coronary artery disease and the normal control. Peak filling rate was decreased significantly in the groups with left anterior descending artery disease (LAD, p less than 0.05) and multivessel disease (MVD, p less than 0.05), but not in the group with right coronary artery disease (RCA). Time to peak filling rate was prolonged in each group of LAD (p less than 0.05), RCA (p less than 0.05), and MVD (p less than 0.001), compared with controls. The time-volume curve showed disturbed rapid filling in the LAD and RCA groups, and also both depressed rapid and slow filling in the MVD group. In the LAD group, the filling fraction was decreased significantly at the time of 25% of the diastolic period (p less than 0.001) and radial distension to the anterior wall was decreased at the time of 25%, 50%, and 75% of the diastolic period, compared with controls. In the RCA group, the filling fraction (p less than 0.001) and radial distension to the posterior wall were decreased only at the time of 25% of the diastolic period. In the MVD group, filling fraction and radial distension to the most wall were decreased at 25%, 50%, and 75% of the diastolic period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of relative coronary Doppler flow velocity reserve to stress myocardial perfusion imaging in patients with coronary artery disease.

To compare relative coronary artery vasodilator reserve (rCVR = CVRtarget/CVRreference) to myocardial perfusion stress imaging, 48 patients with coronary artery stenoses (61% +/- 16%; mean, +/- SD; range, 30%-91%) had measurements of target and reference vessel CVR (Doppler-tipped guidewire). rCVR was computed and compared to stress 201thallium or (99m)technetium-sestamibi myocardial tomography. Compared to 24 patients with negative stress imaging studies, 24 patients with positive stress studies had angiographically more severe stenoses (74% +/- 13% vs. 44% +/- 24%; P = 0.0005) with lower CVR(target) (1.68 +/- 0.55 vs. 2.46 +/- 0.74; P = 0.002) and lower rCVR (0.72 +/- 0.22 vs. 1.0 +/- 0.26; P < 0.003). Based on receiver-operator characteristic (ROC) cut points (CVR > 1.9; rCVR > 0.75), compared to CVR, rCVR had similar agreement (Kappa 0.54 vs. 0.50), sensitivity (63% vs. 71%), specificity (88% vs. 83%), and positive predictive value (83% vs. 81%) with myocardial perfusion tomography. A concordant CVRtarget/rCVR only slightly increased sensitivity, specificity, and positive predictive values (77%, 90%, and 87%, respectively). Although rCVR, like CVR, correlates with stress myocardial perfusion imaging results, rCVR did not have significant incremental prognostic value over CVR alone for myocardial perfusion imaging. However, rCVR does provide additional information regarding the status of the microcirculation in patients with coronary artery disease and complements the CVR for lesion assessment.     

Effects of oxyfedrine on regional myocardial blood flow in patients with coronary artery disease

Summary Medical treatment of angina pectoris is largely based on the use of beta-blocking agents, calcium antagonists, and nitrates. Oxyfedrine, an amino ketone derivative and partial agonist at beta receptors, has been shown to have potent antianginal properties and to increase coronary blood flow in normal and ischemic myocardial regions in experimental studies. We assessed the effects of intravenous oxyfedrine on regional myocardial blood flow, using positron emission tomography (15-oxygen water), in six patients with chronic stable angina, positive exercise tests, and documented coronary artery disease. Myocardial blood flow was measured in all patients before (baseline) and 10 minutes after the intravenous administration of a single bolus (0.11–0.13 mg/kg) of oxyfedrine. Compared to baseline, heart rate and systolic blood pressure remained almost unchanged after the administration of oxyfedrine. Mean baseline myocardial blood flow was 0.90±0.15 ml/g/min in areas supplied by arteries with significant coronary stenosis and 1.08±0.19 ml/g/min in areas supplied by nonstenotic coronary vessels (p<0.05). After the adminsitration of oxyfedrine, myocardial blood flow increased significantly in both the regions supplied by stenotic vessels (by 25%; from 0.90±0.15 to 1.20±0.31 ml/g/min; p=0.002) and in areas supplied by angiographically normal coronary vessels (by 22%; from 1.08±0.19 to 1.38±0.49 ml/g/min; p<0.05). The results of this study indicate that in patients with coronary artery disease, intravenous oxyfedrine significantly increases regional myocardial blood flow, both in areas supplied by critically obstructed vessels and in areas supplied by normal or less severely narrowed coronary arteries.     

Effect of carbocromen induced coronary vasodilatation on myocardial metabolism in coronary artery disease

Myocardial metabolism was studied during coronary vasodilatation by carbocromen during atrial pacing in patients with coronary arteriosclerotic disease. Coronary sinus flow was measured by the continuous infusion thermodilution technique. Carbocromen increased myocardial flow by the same amount at rest and during pacing-induced tachycardia. The administration of carbocromen did not interfere with myocardial oxygen consumption, free fatty acid (FFA) uptake, pulmonary or systemic hemodynamics. Atrial pacing above the anginal threshold increased lactate and hypoxanthine excretion to the coronary sinus, but to a greater extent during carbocromen treatment. Thus, carbocromen is a specific coronary vasodilator acting independently of pacing induced vasodilatation. Metabolic data indicate a small but unfavourable effect on ischemic metabolism which might be due to a “coronary steal”.     

不同程度狭窄病变冠心病患者介入治疗后心肌灌注变化及临床意义

目的利用经冠状动脉超声心肌声学造影（MCE）比较单支血管不同程度狭窄病变冠心病患者经皮冠状动脉介入术（PCI）后心肌灌注的变化,并探讨其临床意义。方法62例进行PCI治疗的住院患者根据选择性冠状动脉造影结果,按血管狭窄程度分组:A组,血管狭窄75%95%;B组,血管狭窄>95%;C组,急性血管闭塞。PCI前及术后15 min进行经冠状动脉MCE,检测心肌灌注状况。其中,MCE有关定量参数分别为:造影剂峰值密度反映心肌血容量;峰值时间反映心肌灌注速度;曲线下面积反映心肌血流量。结果所有患者PC I后均达到TIMIⅢ级血流;A组术后心肌血流量较术前增加（P<0.05）;B组心肌血容量及血流量也较术前增加（P<0.05）;而C组心肌血容量、血流量及灌注速度较术前增加更显著（P<0.01）。结论不同狭窄程度病变冠心病患者,PCI后心肌灌注均得到不同程度改善,其中,以急性闭塞病变改善最明显,该类患者为PCI治疗的最大获益者。     

早发心肌梗死患者的临床危险因素及冠脉病变特点分析

目的：探讨早发心肌梗死患者的临床危险因素及冠脉病变特点。方法：采用回顾性研究方法,2014年8月到2016年5月选择在我院诊治早发心肌梗死(男性<55岁或女性<65岁)患者40例作为观察组,同期选择在我院诊治的非早发心肌梗死患者89例作为对照组,记录两组的冠脉病变特点,调查临床资料并进行危险因素分析。结果：观察组冠脉病变以单支病变为主,对照组主要为多支病变(P<0.05)。Logistic回归分析结果显示LDL-C、吸烟史及冠心病家族史是早发心肌梗死的独立危险因素(P<0.05)。观察组的心力衰竭、恶性心律失常、心源性休克等主要心脏不良事件发生率5.0%,对照组为16.8%,观察组明显低于对照组(P<0.05)。住院期间病死率观察组为5.0%,对照组为11.2%,观察组明显低于对照组(P<0.05)。结论：早发心肌梗死患者的冠脉病变以单支病变为主,LDL-C、吸烟史及冠心病阳性家族史是早发心肌梗死的独立危险因素;早发心肌梗死患者住院期间病死率低,预后好。     

Short-term effects of atrial versus atrio-ventricular pacing on myocardial ischaemia in coronary artery disease patients

This investigation was undertaken to evaluate the effects ofshort-term atrial vs atrio-ventricular pacing on myocardialischaemia. The study was in two parts. In part one, 12 coronary arterydisease patients were studied to investigate the effects ofthe two pacing modes on angina pectoris, coronary sinus O₂ saturationand lactate. The two pacing modes were each applied for 5 minat 25 beats. min^–1 more than the maximum heart rate ofthe exercise test. Coronary sinus O₂ saturation and lactatewere estimated before and after pacing. In part two, 13 patientswith left anterior descending coronary artery disease were studiedto investigate the effects of the two pacing modes on coronaryflow reserve, using a Doppler catheter in the above mentionedbranch after the administration of 10 mg intracoronary papaverine.The pacing rate was 15 beats . min^–1 greater than theresting heart rate. Coronary sinus lactate and O₂ saturation changes were the sameand angina pectoris developed at about the same time from thebeginning of pacing under both modes. Coronary flow reservewas 2.1±0.7 during atrial pacing and 2.1±1.1 duringatrio-ventricular pacing (ns). It is concluded that short-term atrial and atrio-ventricularpacing have the same effects on myocardial ischaemia in coronaryartery disease patients.     

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。     

Disopyramide improves the balance between myocardial oxygen supply and demand in patients with hypertrophic obstructive cardiomyopathy

Summary We evaluated the effects of disopyramide in terms of the balance between myocardial oxygen supply and demand in patients with hypertrophic obstructive cardiomyopathy (HOCM). The myocardial oxygen supply was evaluated by measuring coronary flow velocity and the myocardial oxygen demand was assessed by the pressure-volume area (PVA). The time velocity integral of coronary flow did not change significantly (20±6 to 21±8 cm), but the peak left ventricular pressure and left ventricular external work decreased significantly (206±44 to 157±37 mmHg,P<0.001; 1.09±0.33 to 0.80±0.23 J/beat,P<0.001) after disopyramide administration. From theoretical analysis using these data, we concluded that disopyramide improves the myocardial oxygen supply-demand balance in patients with HOCM.     

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.)     

核素心肌显像测定MBF和CFR在冠心病的诊断价值及展望

心血管疾病是世界范围内最主要的死亡原因,其治疗和诊断的经济成本很高,在过去的20年里,对冠心病患者诊断、评估及治疗越来越准确和有效。正电子发射断层显像技术是一种强大而多功能的无创性影像学检查,特别是通过量化心肌血流量(MBF)及冠状动脉血流储备(CFR)可以更好地描述冠状动脉疾病的特征,在冠状动脉微血管病变及缺血性心肌病的早期诊断、分级及治疗中发挥着重大作用。     

A critical look at currently used indirect indices of myocardial oxygen consumption

Summary Myocardial oxygen consumption indices that are frequently applied to man such as tension-time index (TTI), pressure-rate product (P·HR) and triple product (TP) have not been fully validated so far. These easily obtainable indices and a modified TTI , therefore, were examined in 10 closed-chest dogs with very broad variations of hemodynamics and oxygen consumption (3–36 ml/min·100 g) analyzing 162 steady states. Myocardial blood flow was directly measured by a differential pressure coronary sinus catheter. was varied by administration of catecholamines and other inotropic drugs, atropine, beta-blocking agents and hypo- and hypervolemia. Over a wide range of hemodynamic states, correlations with directly measured of TTI (r=0.63), P·HR (r=0.87), TP (r=0.65) and (r=0.80) are not satisfactory due to neglect of contractility and cardiac volumes by these terms. Better correlations are obtained when relating these indices to under different inotropic states. At normal and moderately increased contractility, correlations with rose as follows: TTI (r=0.96), P·HR (r=0.91), TP (r=0.96) and (r=0.94). Significant rises in correlation are due to the close relationship between peak pressure and dP/dt_max at only moderately increased contraction velocity. Correlation differences within this inotropic range must be related to incorporation or neglect of ejection time as a partial determinant of . At markedly increased contractility, results for these indices, however, are in part very poor: TTI (r=0.40), P·HR (r=0.81), TP (r=0.38) and (r=0.76). Within this inotropic state neglect of dP/dt_max as a major determinant of and the inverse relationship between ejection time and dP/dt_max mainly account for these correlation shifts. It is concluded that non-invasively obtainable indices, currently in use, are no reliable predictors of actual overall of the left ventricle if the contractile state of the myocardium is not checked invasively before. The broad variability of the relation of the energy demand of velocity of tension development to maintenance of systolic wall tension is not sufficiently considered by these terms. Appropriate caution, therefore, is necessary when applying those indirect indices of to humans.Supported by the Deutsche Forschungsgemeinschaft, SFB 89, Kardiologie, Göttingen