Role of cardiac imaging in heart failure.

Heart failure is the leading cause of mortality and rehospitalization in Western countries. With the development of new technologies applied to medical diagnostic pathways, cardiovascular imaging has rapidly gained ground. Therefore, the clinical cardiologist has to keep updated on the management of such innovative diagnostic tools which were once the exclusive domain of radiologists. The need to understand a new language is fundamental for the selection of diagnostic and therapeutic strategies in patients with heart failure, which is often the final destination for many cardiovascular diseases. Alongside standard diagnostic techniques such as chest radiography two-dimensional ultrasound and cardiac color Doppler, all of which are indispensable in daily practice, innovative tools have been defining their incremental role in cardiovascular imaging. Cardiac magnetic resonance (CMR), cardiac computed tomography (CT), speckle tracking, 3D echocardiography, new applications in nuclear medicine (SPECT MIBG), and "cardiac hybrid imaging" are emerging for research and are also playing a pivotal role in the clinical scenario. These techniques are useful the for non-invasive acquisition of diagnostic and prognostic information in heart failure. Whether the radiological and economic impact of these new technologies is sustainable is a question the clinical cardiologist will need to answer when considering the cost/benefit of the diagnostic tool selected among these methods.

Techniques for transvenous leads extraction.

The number of implanted cardiac pacing and defibrillating devices is currently increasing, leading to an increasing number of device-related complications, due to either malfunction or infection. Removal of the whole system, including the leads, was proven to be the most effective therapy. At present the importance of transvenous lead extraction is consequently increased. In order to remove pacing and implantable cardioverter defibrillators (ICD) leads, they have to be made free from any binding site from the entry in the vein to the tip. Different techniques, including mechanical dilation, powered dilation and intravascular approaches have been developed over the last years and are currently available. Results reported in the literature show a significant success rate (ranging between 90% and 98% of the leads) and a reduced incidence of serious complications (1% to 3% in different series) in selected centres. The extraction procedures are complex and life-threatening complications may always occur, suggesting the need of trained and experienced operators as well as the availability of a surgical standby. At present indications to removal are restricted to infection or to damage of the leads inducing serious risk for the patients; the availability of a more effective and safe technique will probably spread indications to most of abandoned leads.

Determination of volatile organic compounds in exhaled breath of heart failure patients by needle trap micro-extraction coupled with gas chromatography-tandem mass spectrometry.

The analytical performances of needle trap micro-extraction (NTME) coupled with gas chromatography-tandem mass spectrometry were evaluated by analyzing a mixture of twenty-two representative breath volatile organic compounds (VOCs) belonging to different chemical classes (i.e. hydrocarbons, ketones, aldehydes, aromatics and sulfurs). NTME is an emerging technique that guarantees detection limits in the pptv range by pre-concentrating low volumes of sample, and it is particularly suitable for breath analysis. For most VOCs, detection limits between 20 and 500 pptv were obtained by pre-concentrating 25 ml of a humidified standard gas mixture at a flow rate of 15 ml min-1. For all compounds, inter- and intra-day precisions were always below 15%, confirming the reliability of the method. The procedure was successfully applied to the analysis of exhaled breath samples collected from forty heart failure (HF) patients during their stay in the University Hospital of Pisa. The majority of patients (about 80%) showed a significant decrease of breath acetone levels (a factor of 3 or higher) at discharge compared to admission (acute phase) in correspondence to the improved clinical conditions during hospitalization, thus making this compound eligible as a biomarker of HF exacerbation.

Beneficial effects of intracoronary adenosine as an adjunct to primary angioplasty in acute myocardial infarction.

BACKGROUND: The benefits of vessel recanalization in acute myocardial infarction (AMI) are limited by reperfusion damage. In animal models, adenosine limits reperfusion injury, reducing infarct size and improving ventricular function. The aim of this study was to evaluate the safety and feasibility of adenosine adjunct to primary PTCA in AMI. METHODS AND RESULTS: Fifty-four AMI patients undergoing primary PTCA were randomized to intracoronary adenosine or saline. The 2 groups were similar for age, sex, and infarct location. Adenosine administration was feasible and well tolerated. PTCA was successful in all patients and resulted in TIMI 3 flow in all patients given adenosine and in 19 given saline (P<0.05). The no-reflow phenomenon occurred in 1 adenosine patient and in 7 saline patients (P=0.02). Creatine kinase was lower in the adenosine group, and a Q-wave MI developed in 16 adenosine patients and in 23 saline patients (P=0.04). Sixty-four percent of dyssynergic segments improved in the adenosine group and 36% in the saline group (P=0. 001). Function worsened in 2% of dysynergic segments in the adenosine group and in 20% in the saline group (P=0.0001). Adverse cardiac events occurred in 5 patients in the adenosine group and in 13 patients in the saline group (P=0.03). CONCLUSIONS: Intracoronary adenosine administration is feasible and well tolerated in AMI. Adenosine adjunct to primary PTCA ameliorates flow, prevents the no-reflow phenomenon, improves ventricular function, and is associated with a more favorable clinical course.

Paradoxical increase in microvascular resistance during tachycardia downstream from a severe stenosis in patients with coronary artery disease : reversal by angioplasty.

BACKGROUND: The pathophysiology of microvascular response to a severe coronary stenosis has not been conclusively identified. The aim of this study was to characterize the human vasomotor response to pacing-induced ischemia of both the stenotic arterial segment and the distal microcirculation. METHODS AND RESULTS: Sixteen patients with stable angina and single-vessel disease were studied. Blood flow velocity and transstenotic pressure gradient were monitored at baseline, after intracoronary adenosine (2 mg), and during ischemia induced by atrial pacing with and without adenosine. At the end of this protocol, the study was repeated after intracoronary phentolamine in 7 patients and after angioplasty in 9. Stenosis resistance was calculated as the ratio between mean pressure gradient and mean flow, and microvascular resistance as the ratio between mean distal pressure and mean flow; values were expressed as percent of baseline. Adenosine decreased (P<0.05) baseline microvascular resistance to 52+/-17%, but not stenosis resistance. Pacing increased both stenosis and microvascular resistances (244+/-96% and 164+/-60% of baseline, respectively, P<0.05). Addition of adenosine to pacing decreased both stenosis (143+/-96% of baseline, P<0.05 versus ischemia) and microvascular (51+/-17% of baseline, P<0.05 versus baseline and ischemia) resistances. Phentolamine did not affect coronary resistance at any step of the protocol. Angioplasty and stenting restored a progressive decline in microvascular resistance during pacing (51+/-19% of baseline, P<0.05 versus baseline). CONCLUSIONS: In patients with coronary artery disease, tachycardia-induced ischemia was associated with elevated resistance of both the stenotic segment and the microvasculature. Revascularization prevents this paradoxical behavior.

Coronary microcirculatory vasoconstriction during ischemia in patients with unstable angina.

OBJECTIVE: To verify the behavior of coronary microvascular tone during spontaneous ischemia in patients with unstable angina (UA). BACKGROUND: In UA, the pathogenetic role of vasoconstriction is classically confined at the stenotic coronary segment. However, microcirculatory vasoconstriction has been also suggested by previous experimental and clinical studies. METHODS: The study included 10 patients with UA (recent worsening of anginal threshold and appearance of angina at rest) and single-vessel CAD. Blood flow velocity was monitored by a Doppler catheter in the diseased artery. Transstenotic pressure gradient was monitored by aortic and distal coronary pressure monitoring. Stenosis resistance was calculated as the ratio between pressure gradient and blood flow, microvascular resistance as the ratio between distal pressure and blood flow. Measurements were obtained at baseline, following intracoronary adenosine (2 mg) and during transient ischemia. Aortic and distal coronary pressures were also measured during balloon coronary occlusion. RESULTS: Adenosine did not affect stenosis resistance, while it decreased (p < 0.05) microvascular resistance to 52 +/- 22% of baseline. Angina and ischemic ST segment shift were associated with transient angiographic coronary occlusion in 7 of 10 patients; however, in no case was ischemia associated with interruption of flow. Despite markedly different flow values, distal coronary pressure was similar during adenosine and during spontaneous ischemia (48 +/- 15 vs. 46 +/- 20 mm Hg, respectively, NS). During ischemia, a marked increase in the resistance of both coronary stenosis and coronary microcirculation was observed (to 1,233% +/- 1,298% and 671% +/- 652% of baseline, respectively, p < 0.05). Distal coronary pressure was markedly reduced during balloon coronary occlusion (14 +/- 7 mm Hg, p < 0.05 vs. both adenosine and ischemia), suggesting the absence of significant collateral circulation. CONCLUSIONS: In patients with UA, transient myocardial ischemia is associated with vasoconstriction of both stenotic arterial segment and downstream microcirculation.

"Ischemia at a distance" during intermittent coronary artery occlusion: a coronary anatomic explanation.

The mechanism of electrocardiographic ST segment changes during acute coronary occlusion was evaluated in 28 consecutive patients with single vessel coronary artery disease undergoing coronary angioplasty. Patients were continuously monitored with a six lead electrocardiogram. Twenty-three patients showed ST changes in the primary zone of occlusion, and 13 of these had additional ST changes in a remote zone. Ten of these 13 had unusually extensive arteries supplying the remote zone. The balloon occluded two adjacent normal arteries in two patients, and no coronary anatomic explanation was evident in one patient. Ten patients with striking primary zone ST changes showed no remote change. Seven had nonextensive primary zone arteries, and three others had abundant collateral vessels. Five patients showed no electrocardiographic changes in primary or remote zones. Four had collateral vessels, and one had left ventricular hypertrophy on the baseline electrocardiogram. It was concluded that remote electrocardiographic changes are probably due to occlusion of unusually extensive coronary arteries and are not simply reciprocal.

Coronary vasodilation by nitrates is not mediated by the prostaglandin system: a quantitative cineangiographic study.

The possible role of prostaglandins in mediating large coronary artery vasodilation by nitrates was investigated by quantitative magnification coronary angiography. The effects of aspirin (1 g systemically and 100 mg intracoronary) in preventing large coronary artery vasodilation induced by intracoronary isosorbide dinitrate was investigated in 16 patients. Of these, 5 received 0.3 mg (Group 1A) and 11 received 3 mg (Group 1B) intracoronary isosorbide dinitrate, before and 15 minutes after aspirin. Relative to control, 0.3 mg isosorbide dinitrate induced a 19 +/- 9% (mean +/- SD) (p less than 0.01) and 19.5 +/- 11% (p less than 0.01) increase in coronary diameter before and after aspirin, respectively (p = NS). Changes after 3 mg isosorbide were 23 +/- 12% (p less than 0.01) and 26.5 +/- 14% (p less than 0.01), respectively, before and after aspirin (p = NS). In 10 additional patients (Group 2), the effect of the same dose of aspirin on rest coronary artery tone was assessed: changes relative to control were 0.9 +/- 5.5% (p = NS) minutes after aspirin. The intracoronary administration of 3 mg isosorbide dinitrate produced a 24.7 +/- 11% increase in coronary diameter (p = NS versus pre- and postaspirin isosorbide in Group 1B). Urinary 6-ketoprostaglandin-F1 alpha values in urine samples collected in the 8 hours before and the 8 hours after the study in five patients in Group 1B and five patients of Group 2, revealed a 36 +/- 14% (mean +/- SD) reduction in excretion of prostacyclin (p less than 0.01). These data rule out a role for prostaglandins both in mediating dilation of large coronary arteries by nitrates and in affecting their vascular tone at rest.

Transient myocardial dysfunction during pharmacologic vasodilation as an index of reduced coronary reserve: a coronary hemodynamic and echocardiographic study.

Regional coronary flow reserve and regional myocardial contractility were evaluated in 29 patients after maximal pharmacologic coronary vasodilation (intravenous dipyridamole, 0.56 mg/kg body weight, administered over 4 minutes). Nineteen patients had a severe (80 to 99%) proximal and isolated stenosis of the left anterior descending coronary artery and 10 patients had normal coronary arteries; all had normal ventricular function under rest conditions. Myocardial contractility was assessed by means of continuous two-dimensional echocardiographic monitoring; coronary reserve was evaluated by coronary sinus thermodilution. After dipyridamole infusion, 9 of the 19 patients with left anterior descending artery stenosis had transient myocardial asynergy involving the septum or apex, or both (Group IA), whereas 10 patients showed no asynergy (Group IB). No impairment of contractility was observed in the 10 patients with normal coronary arteries (Group II). Coronary blood flow was measured under basal conditions and up to 10 minutes after the end of dipyridamole infusion. In patients in Group II, dipyridamole induced an increase in great cardiac vein flow of 167 +/- 68% (mean +/- SD). The 10 patients in Group IB showed a response comparable with that of the control group (Group II) (136 +/- 45% increase in great cardiac vein flow; NS versus Group II), whereas the 9 patients in Group IA had an increase of 46 +/- 30% (p less than 0.01 versus both Group IB and Group II). No significant difference was found in the angiographic severity of the stenosis expressed in terms of minimal cross-sectional area (Group IA = 0.30 +/- 0.13 mm2, Group IB = 0.34 +/- 0.18 mm2; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary hemodynamics and myocardial metabolism in patients with syndrome X: response to pacing stress.

Coronary hemodynamics, myocardial metabolism and left ventricular function at rest and after incremental atrial pacing were evaluated in 12 patients with stress-induced angina and ST segment depression, angiographically normal coronary arteries and no evidence of spasm, generally labeled as syndrome X, and in 10 normal subjects. At baseline study, great cardiac vein flow was comparable in patients and control subjects. During pacing, an equivalent rate-pressure product was reached in the two groups, but the slope of the relation between rate-pressure product and great cardiac vein flow was significantly less steep in patients than in normal subjects (0.0027 vs. 0.0054 ml/mm Hg.beat, p less than 0.001). Nevertheless, the left ventricular ejection fraction was comparable in both groups at rest (66 +/- 6% vs. 71 +/- 7%, p = NS) and during pacing (71 +/- 7% vs. 66 +/- 5%, p = NS). At baseline study, myocardial glucose extraction was more efficient in patients with syndrome X (p less than 0.05), but net myocardial exchange of pyruvate and alanine was, respectively, smaller and greater than in control subjects. Lactate was extracted to a similar extent in the two groups and in no instance was net lactate release observed during pacing or recovery. During pacing and recovery, patients with syndrome X showed net pyruvate release, unlike the control subjects in whom net pyruvate exchange was positive. In addition, patients with syndrome X continued to show net myocardial extraction of alanine during spacing and recovery, whereas normal subjects produced alanine throughout the study. Myocardial carbohydrate oxidation increased significantly during maximal pacing in normal subjects but not in patients, in whom it always remained below (p less than 0.01) the concurrent rate of myocardial uptake of carbohydrate equivalents (glucose, lactate, pyruvate, alanine). Myocardial energy expenditure was significantly lower in patients than in control subjects at maximal rate-pressure product levels (p less than 0.01). The metabolic pattern in patients with syndrome X therefore is not consistent with classic ischemia, although differences in the net exchange of circulating substrates (glucose, pyruvate, alanine) can be demonstrated. Thus, in patients with syndrome X, the symptoms, electrocardiographic signs and impairment in the increase in great cardiac vein flow during pacing coexist with preserved global and regional left ventricular function and myocardial energy efficiency.

Microvascular dysfunction in collateral-dependent myocardium.

OBJECTIVES: The aim of this study was to evaluate myocardial blood flow regulation in collateral-dependent myocardium of patients with coronary artery disease. BACKGROUND: Despite great clinical relevance, perfusion correlates of collateral circulation in humans have rarely been estimated by quantitative methods at rest and during stress. METHODS: Nineteen patients with angina and isolated occlusion of the left anterior descending (n = 14) or left circumflex (n = 5) coronary artery were evaluated. Using positron emission tomography and nitrogen-13 ammonia, we obtained flow measurements at baseline, during atrial pacing-induced tachycardia and after intravenous administration of dipyridamole (0.56 mg/kg body weight over 4 min). Flow values in collateral-dependent and remote areas were compared with values in 13 normal subjects. RESULTS: Flow at rest was similar in collateralized and remote myocardium (0.61 +/- 0.11 vs. 0.63 +/- 0.17 ml/min per g, mean +/- 1 SD), and both values were lower than normal (1.00 +/- 0.20 ml/min per g, p < 0.01). During pacing, blood flow increased to 0.83 +/- 0.25 and 1.11 +/- 0.39 ml/min per g in collateral-dependent and remote areas, respectively (p < 0.05 vs. baseline); both values were lower than normal (1.86 +/- 0.61 ml/min per g, p < 0.01). Dipyridamole induced a further increase in perfusion in remote areas (1.36 +/- 0.57 ml/min per g, p < 0.01 vs. pacing) but not in collateral-dependent regions (0.93 +/- 0.37 ml/min per g, p = NS vs. pacing); again, both values were lower (p < 0.01) than normal (3.46 +/- 0.78 ml/min per g). Dipyridamole flow in collateral-dependent myocardium was slightly lower in patients with poorly developed than in those with well developed collateral channels (0.75 +/- 0.29 vs. 1.06 +/- 0.38 ml/min per g, respectively, p = 0.06); however, the former showed higher flow inhomogeneity (collateral/control flow ratio 0.58 +/- 0.10 vs. 0.81 +/- 0.22, respectively, p < 0.02). A linear direct correlation was observed between flow reserve of collateral-dependent and remote regions (r = 0.83, p < 0.01). CONCLUSIONS: Despite rest hypoperfusion, collateral-dependent myocardium maintains a vasodilator reserve that is almost fully utilized during increases in oxygen consumption. A global microvascular disorder might hamper adaptation to chronic coronary occlusion.

Adenosine causes the release of active renin and angiotensin II in the coronary circulation of patients with essential hypertension.

OBJECTIVES: The aim of the study was to evaluate whether adenosine infusion can induce production of active renin and angiotensin II in human coronary circulation. BACKGROUND: Adenosine can activate angiotensin production in the forearm vessels of essential hypertensive patients. METHODS: In six normotensive subjects and 12 essential hypertensive patients adenosine was infused into the left anterior descending coronary artery (1, 10, 100 and 1,000 microg/min x 5 min each) while active renin (radioimmunometric assay) and angiotensin II (radioimmunoassay after high performance liquid chromatography purification) were measured in venous (great cardiac vein) and coronary arterial blood samples. In five out of 12 hypertensive patients adenosine infusion and plasma samples were repeated during intracoronary angiotensin-converting enzyme inhibitor benazeprilat (25 microg/min) administration. Finally, in adjunctive hypertensive patients, the same procedure was applied during intracoronary sodium nitroprusside (n = 4) or acetylcholine (n = 4). RESULTS: In hypertensive patients, but not in control subjects, despite a similar increment in coronary blood flow, a significant (p < 0.05) transient increase of venous active renin (from 10.7 +/- 1.4 [95% confidence interval 9.4 to 11.8] to a maximum of 13.8 +/- 2.1 [12.2 to 15.5] with a consequent drop to 10.9 +/- 1.8 [9.7 to 12.1] pg/ml), and angiotensin II (from 14.6 +/- 2.0 [12.7 to 16.5] to a maximum of 20.4 +/- 2.7 [18.7 to 22.2] with a consequent drop to 16.3 +/- 1.8 [13.9 to 18.7] pg/ml) was observed under adenosine infusion, whereas arterial values did not change. Calculated venous-arterial active renin and angiotensin II release showed a strong correlation (r = 0.78 and r = 0.71, respectively; p < 0.001) with circulating active renin. This adenosine-induced venous angiotensin II increase was significantly blunted by benazeprilat. Finally, both sodium nitroprusside and acetylcholine did not affect arterial and venous values of active renin and angiotensin II. CONCLUSIONS: These data indicate that exogenous adenosine stimulates the release of active renin and angiotensin II in the coronary arteries of essential hypertensive patients, and suggest that this phenomenon is probably due to renin release from tissue stores of renally derived renin.

The atropine factor in pharmacologic stress echocardiography. Echo Persantine (EPIC) and Echo Dobutamine International Cooperative (EDIC) Study Groups.

OBJECTIVES: This study sought to compare, head to head, the two most popular pharmacologic stress echocardiographic tests--dipyridamole and dobutamine--with state of the art protocols in a large multicenter prospective study. BACKGROUND: In the continuing quest for ideal diagnostic accuracy, pharmacologic stress echocardiography has quickly moved over the years from low to high dose regimens and is currently performed with atropine coadministration. METHODS: Dobutamine (up to 40 microgram/kg body weight per min) plus atropine (up to 1 mg over 4 h) and dipyridamole (up to 0.84 mg/kg per min over 10 h) plus atropine (up to 1 mg over 4 h) stress echocardiography was performed on different days, in random order and within 1 week in 360 patients with chest pain syndrome. Thirteen different echocardiographic laboratories, all fulfilling quality control criteria for stress echocardiographic reading, contributed to the study. RESULTS: No major complications occurred during either test. The test was interrupted before achievement of predetermined end points for limiting side effects in 37 dobutamine-atropine and 7 dipyridamole-atropine stress echocardiographic studies (feasibility 90% vs. 98%, p < 0.01). Diagnostic accuracy was assessed in a subset of 110 patients with no obvious rest dyssynergy (akinesia or dyskinesia) who underwent coronary angiography independently of test results and within 1 week of testing. Significant coronary artery disease (> or = 50% diameter reduction in at least one major coronary vessel by quantitative coronary angiography) was found in 92 patients. Sensitivity for detection of coronary artery disease was 84% (77 of 92) for dobutamine-atropine and 82% (75 of 92) for dipyridamole-atropine stress echocardiography (p = NS), with a specificity of 89% (16 of 18) for dobutamine-atropine and 94% (17 of 18) for dipyridamole-atropine stress echocardiography (p = NS). A significant correlation was present between peak wall motion score index during dipyridamole-atropine and dobutamine-atropine stress echocardiography (r = 0.83, p < 0.0001). CONCLUSIONS: Dobutamine-atropine and dipyridamole-atropine stress echocardiography are safe and feasible, although submaximal studies are more frequent with dobutamine. The two stresses have comparable accuracy in the detection of angiographically assessed coronary artery disease, although dobutamine is marginally more sensitive and dipyridamole marginally more specific. Stratification of the ischemic response in the space domain is also comparable with the two stresses.

Adenosine-induced renal vasoconstriction in man.

OBJECTIVE: The aim of the study was to evaluate the effects of adenosine on renal blood flow in humans. METHODS: Eleven normotensive patients (mean age 53 +/- 11 years) with normal renal angiograms were enrolled in the study. Arterial blood pressure, one ECG lead and arterial renal blood flow velocity, by intravascular Doppler catheter, were monitored throughout the procedure. Incremental doses (10(-5), 10(-4), 10(-3), 2 x 10(-3), 5 x 10(-3), 10(-2), 10(-1), 1 mg) were selectively injected, at 5-min intervals, in a renal artery. RESULTS: Adenosine administration had no significant effects on blood pressure, heart rate and atrio-ventricular conduction. A progressive reduction in renal blood flow velocity (from 16.36 +/- 1.9 to 3.9 +/- 0.8 cm/s, P < 0.0001) was observed. Following adenosine the decrease of flow velocity was immediate and its duration was proportional to dosage (from 0.5 +/- 0.4 s at 10(-5) mg to 31 +/- 6.5 s at 1 mg). Renal angiography, repeated in four patients during flow velocity decrement, showed no changes in vessel diameter. CONCLUSIONS: Exogenous adenosine-induced a marked and transient reduction in renal blood flow in man. This effect suggests that adenosine or its metabolites may be directly implicated in rapid and powerful mechanisms of cardiac output redistribution. Thus endogenous adenosine could have a role in regulating renal blood flow in physiological and pathological situations like strenuous exercise, hemorrhage shock and cardiac failure.

Persistence of subendocardial perfusion after subtotal coronary embolisation.

The effects of acute subtotal embolisation of small coronary arteries on regional coronary flow and vasodilator reserve were investigated in seven open chest dogs. Unlabelled plastic microspheres (26(2) micron in diameter) were injected as boluses of 200,000-400,000 microspheres into the circumflex artery. Embolisation was repeated until reactive hyperaemia was totally abolished, which occurred after the injection of 62,000(4000) microspheres per gram. Intracoronary adenosine was then infused for 20 min at 1.2 mg.min-1. Regional myocardial blood flow was measured by radioactive microspheres under control conditions, after coronary embolisation, and during adenosine infusion. Coronary blood flow (0.98(0.07) ml.min-1.g-1) was reduced to 0.66(0.08) ml.min-1.g-1 after embolisation (p less than 0.005) when reactive hyperaemia was practically abolished. Embolisation reduced epicardial flow from 0.93(0.08) to 0.40(0.09) ml.min-1.g-1 (p less than 0.001), whereas endocardial flow was unchanged (1.03(0.11) vs 0.92(0.14) ml.min-1.g-1; NS); as a consequence, the endocardial to epicardial flow ratio increased from the control value of 1.11(0.06) to 2.31(0.35) (p less than 0.005). Adenosine infusion increased coronary blood flow from 0.66(0.08) to 1.66(0.41) ml.min-1.g-1 (p less than 0.05). Endocardial blood flow increased more than epicardial blood flow, leading to a further increase in the endocardial to epicardial flow ratio (3.79(0.13); p less than 0.05). Thus it is concluded that (a) embolisation of small arteries abolishes the reactive hyperaemic response to transient coronary occlusion; (b) microembolisation predominantly reduces subepicardial perfusion; and (c) adenosine administration may increase total and regional flow after subtotal occlusion of coronary small arteries.

Possibilities, limitations, and technique for the study of regional myocardial perfusion in man by Xenon-133.

The theoretical possibilities and the practical limitations of the Xenon-133 (133Xe) method for the study of regional myocardial perfusion in man are discussed. The techniques for data acqusition and processing developed over the past 5 years are described in detail. Illustrative examples of experimental findings are reported. The practical interpretation of the data, at the light of the influence of injection site, initial tracer distribution, constancy of counting geometry, spatial resolution, and Xenon retention in fat, is presented.

Performance of the failing and nonfailing right ventricle of patients with pulmonary hypertension.

Hemodynamic performance of the right ventricle was measured in 34 patients: 17 with pulmonary hypertension, 9 with pulmonary hypertension and right ventricular failure and 8 control subjects. Among the patients with pulmonary hypertension who did not have right ventricular failure, right ventricular maximal isovolumic rate of development of ventricular pressure (dP/dt) was significantly elevated (P less than 0.001), whereas maximal 1/P dP/dt and maximal velocity of contractile element shortening (Vmax) were comparable with values observed in control subjects. The patients with pulmonary hypertension who had right ventricular failure also showed an augmented right ventricular maximal dP/dt (P less than 0.001) and normal 1/P dP/dt and Vmax. These observations indicate that in pulmonary hypertensive heart disease, even when the right ventricle failed in a clinical sense, the contractile effort was normal. Consequently, right ventricular failure may develop in patients with pulmonary hypertensive heart disease even though the cardiac muscle performs normally as a contractile tissue.

Some clinical considerations regarding the relation of coronary vasospasm to coronary atherosclerosis: a hypothetical pathogenesis.

This study explores the relation between coronary arterial spasm and the development of coronary atherosclerosis. The clinical history and coronary angiographic and electrocardiographic data in 212 consecutive patients with ischemic heart disease were correlated. These patients were classified into four groups: Group 1, patients without angiographic evidence of atherosclerosis; Group 2, patients with single vessel disease; Group 3, patients with double vessel disease; and Group 4, patients with significant narrowing of major coronary arteries. Although spontaneous angina occurred in all four groups, it was more common (55 percent) in the patients in Group 1, who were predominantly female and young. Spontaneous angina was confirmed in Group 1 with several techniques, including thallium-201 scintigraphy, ergonovine administration and electrocardiography during attacks of pain. Prior myocardial infarction was present with similar frequency in all four groups. A patient is discussed whose spontaneously occurring coronary arterial spasm later progressed to fixed arteriosclerotic narrowing requiring coronary bypass surgery. These observations and a review of the literature lend support to the hypothesis that coronary arterial spasm can be a possible antecedent leading to the later development of fixed atherosclerotic coronary arterial obstruction.

Dipyridamole-echocardiography test in patients with exercise-induced ST-segment elevation.

Fourteen consecutive patients with exercise-induced ST-segment elevation in the absence of previous infarction and basal left ventricular asynergy at rest performed a dipyridamole test (infusion of dipyridamole, 0.14 mg/kg/min intravenously for 4 minutes) during 12-lead electrocardiographic (ECG) and 2-dimensional echocardiographic monitoring. In 7 of the 14 patients, dipyridamole infusion consistently induced ST-segment elevation in the leads that showed ST elevation on effort; reversible asynergy (occurring in the region corresponding to the ECG leads with diagnostic changes) could always be documented by echocardiography. In 2 patients dipyridamole induced reversible asynergy in presence of ST-segment depression. In these 9 patients angiography invariably revealed a severe organic stenosis in the coronary artery feeding the region that became transiently asynergic after dipyridamole. In the other 5 patients (all of whom had either spontaneous or ergonovine-induced ST-segment elevation), the dipyridamole test yielded no significant echocardiographic or ECG change; coronary angiography showed absent (2 patients) or significant (3 patients) coronary artery disease. In conclusion, dipyridamole may induce transmural ischemia in humans, as detected by the electrical hallmark of ST elevation; this ECG pattern, in contrast to ST depression, reliably predicts the presence and site of transient regional asynergy. When dipyridamole induces ST-segment elevation, severe basal stenosis is invariably present in the coronary artery supplying the transiently asynergic myocardial region.

Angiographically assessed coronary collateral circulation increases vulnerability to myocardial ischemia during vasodilator stress testing.

In patients with a major coronary vessel occluded, the presence of good coronary collateral circulation increases vulnerability to myocardial ischemia induced by pharmacologic coronary vasodilation. The presence of good collaterals results in a greater frequency, severity, and extent of dipyridamole-induced regional left ventricular dysfunction, consistent with the hypothesis of angiographically assessed collaterals facilitating "steal phenomena" during dipyridamole-induced coronary vasodilation.