Effect of coronary occlusion during percutaneous transluminal angioplasty in humans on left ventricular chamber stiffness and regional diastolic pressure-radius relations

Cardiac release of chemoattractants after ischaemia induced by coronary balloon angioplasty

OBJECTIVE

To investigate the release of chemoattractants after myocardial ischaemia during balloon angioplasty.

DESIGN

Sampling of femoral arterial and coronary sinus blood before and immediately after the first balloon inflation during angioplasty. In a study group of 16 patients the balloon was kept expanded for two minutes, whereas in a control group of eight patients the first balloon inflation was brief (< 10 s).

MAIN OUTCOME MEASURES

Chemotaxis of neutrophils from healthy donors towards patient plasma (Boyden chamber), superoxide anion production by normal neutrophils after incubation with patient plasma (cytochrome C reduction).

RESULTS

In the study group, coronary sinus plasma after balloon deflation was more chemoattractive to normal neutrophils (median relative increase 24% (quartiles: 4%, 45%), p = 0.008) and induced a higher superoxide anion production in normal neutrophils (44% (10%, 97%), p = 0.013) than arterial plasma. Concomitantly, the degree of activation of patient neutrophils was increased in coronary sinus blood compared with arterial blood, as shown by an increased proportion of neutrophils reducing nitro-blue tetrazolium (21% (9%, 38%), p = 0.006) and a decreased neutrophil filter-ability (-16%(-3%, -40%), p = 0.003) in coronary sinus blood. In the study group before balloon inflation and in the control group before and after balloon inflation differences between arterial and coronary sinus blood were not significant. Signs of ischaemia (lactate release, ST segment changes) were only detected in the study group.

CONCLUSION

After transient myocardial ischaemia during balloon angioplasty there is a local release of chemoattractants, associated with neutrophil activation.

Does the myocardium become "stunned" after episodes of angina at rest, angina on effort, and coronary angioplasty?

To assess whether myocardial stunning occurs after brief periods of ischemia, global and regional ventricular function assessed by radionuclide angiography was studied in 52 patients. Patients were divided into 3 groups according to the type of ischemic episodes. Group 1 consisted of 15 patients studied before, during and after episodes of angina at rest. Seventeen patients studied immediately before and after coronary angioplasty constituted group 2. Group 3 consisted of 20 patients with stable angina studied before, during and after exercise-induced ischemia. Medical therapy was discontinued 48 hours before the study in all patients except those undergoing coronary angioplasty who were receiving diltiazem 180 mg/day. No difference in baseline ejection fraction was found between groups, whereas peak filling rate was statistically lower in group 3 patients. Evidence of left ventricular dysfunction during ischemia was seen in patients in groups 1 and 3, whereas transient ischemia was documented by ST-segment displacement and/or typical chest pain during balloon inflation in group 2. Persistence of systolic or diastolic dysfunction was not observed in any of the 3 groups in the recovery phase after ischemia. In conclusion, transient ischemia caused either by a primary reduction in oxygen supply (angina at rest, coronary angioplasty) or by an increase in oxygen demand (angina on effort) did not reproduce the phenomenon of systolic and diastolic stunning observed in animal experiments, although in all patients the ischemia was of sufficient duration and severity to induce marked ventricular dysfunction. The search for stunned myocardium should be extended to other different clinical models characterized by prolonged ischemia such as unstable angina or myocardial infarction.

Myocardial stunning: an overview

Over the past two decades, we have challenged the belief that transient ischemia is benign with little functional sequelae following resolution of ischemia. The phenomenon of prolonged postischemic contractile dysfunction, or of myocardial stunning, has been developed and is under investigation using multiple experimental and clinical models. Classifications of myocardial stunning have been suggested and include single and multiple reversible ischemic episodes, partially reversible episodes, and global ischemia. More challenging is the understanding of the mechanisms of myocardial stunning, including free radical protection, excitation-contraction uncoupling, altered calcium flux, microvascular dysfunction, and impaired energy production and use. Finally, advances have been made in the clinical arena, including development of new more sensitive technologies to detect dysfunction, and development of potentially important therapies, including free radical scavengers, adenosine-regulating agents, and calcium channel blockers. In this brief overview, we focus on myocardial stunning, including a historical perspective of coronary occlusion, and definition, classification, and clinical implications of myocardial stunning.

Echocardiographic detection of acute myocardial ischemia during percutaneous transluminal coronary angioplasty

The usefulness of echocardiography and Doppler for the detection of acute myocardial ischemia was evaluated during right coronary artery occlusion in 20 patients. The echocardiographic findings were compared with the occurrence of chest pain, and to electrocardiographic and hemodynamic changes obtained during percutaneous transluminal coronary angioplasty. Our results confirm that, even in the case of small segmental myocardial ischemia, two-dimensional echocardiography is superior to all other measured parameters. In contrast, Doppler examination of transmitral flow is not sensitive enough for the detection of such small segmental myocardial ischemia induced by right coronary artery occlusion.

Does reperfusion injury exist in humans?

Timely coronary reperfusion as treatment for acute myocardial infarction reduces myocardial infarct size, improves left ventricular function and survival. There is still concern that at the time of reperfusion, a further injury occurs to the myocardium. Theoretically, if this "reperfusion injury" could be treated and eliminated, the outcome for patients with myocardial infarction might further improve. The concept of reperfusion injury is closely tied to the concept that oxygen radicals generated at the time of reperfusion cause tissue damage. There are four basic forms of reperfusion injury. Lethal reperfusion injury is described as myocyte cell death due to reperfusion itself rather than to the preceding ischemia. This concept continues to be controversial in both experimental animal and clinical studies. Vascular reperfusion injury refers to progressive damage to the vasculature over time during the phase of reperfusion. Manifestations of vascular reperfusion injury include an expanding zone of no reflow and a deterioration of coronary flow reserve. This form of reperfusion injury has been documented in animal models and probably occurs in humans. Stunned myocardium refers to postischemic ventricular dysfunction of viable myocytes and probably represents a form of "functional reperfusion injury." This phenomenon is well documented in both animal models and humans. Reperfusion arrhythmias represent the fourth form of reperfusion injury. They include ventricular tachycardia and fibrillation that occur within seconds to minutes of restoration of coronary flow after brief (5 to 15 min) episodes of myocardial ischemia. True reperfusion arrhythmias occur in only a small percentage of patients receiving thrombolytic therapy for acute myocardial infarction and are not a sensitive indicator for successful reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology and mediators of ischemia-reperfusion injury with special reference to cardiac surgery. A review

Although necessary for the ultimate tissue survival, reperfusion may paradoxically exacerbate the ischemic injury. Ischemia and reperfusion injury is intimately woven together. The relative role of reperfusion injury is not clarified and probably varies with the ischemic insult: Reperfusion is always preceded by ischemia, and some of the reperfusion-related events may represent a process continuing from the ischemic period; thus the proper designation should be ischemia-reperfusion injury. The reperfusion-related events are: arrhythmias, myocardial stunning with both systolic and diastolic dysfunction, and low reflow and microvascular stunning. Of pathogenetic importance are the mode and speed of reperfusion as well as the initiation of an intracoronary inflammatory reaction during reperfusion, including endothelium-leukocyte interaction, platelets, generation of oxygen free radical, generation and release of arachidonic acid metabolites, platelet activating factor, endothelium derived relaxing factor, endothelins, kinins, and histamine, complement activation, disturbances in calcium homeostasis, and disturbances in lipid and fatty acid metabolism.

Effects of acute, transient coronary occlusion on global and regional right ventricular function in humans

OBJECTIVES

The aim of this study was to investigate the changes in right ventricular function during acute coronary occlusion produced by inflating a coronary angioplasty balloon catheter.

BACKGROUND

Alterations in right ventricular function are well known to occur in patients with acute myocardial infarction or ischemic cardiomyopathy. However, the changes in right ventricular function resulting from acute, transient coronary occlusion of each of the major coronary arteries have been scantily studied, perhaps because of serious limitations of currently available technology.

METHODS

A newly designed, mobile, multiwire gamma camera, in combination with generator-produced tantalum-178, affords high count rate first-pass radionuclide angiography and is thus ideal for studying right ventricular function at the bedside. Accordingly, 46 patients underwent first-pass radionuclide angiography at baseline and during transient coronary occlusion induced by a coronary angioplasty balloon catheter.

RESULTS

A significant, albeit modest, decrease in global right ventricular ejection fraction occurred during occlusion of the left anterior descending (from 42.9 +/- 9.3% to 39 +/- 8.7%, p < 0.05) and left circumflex (from 44 +/- 9.1% to 38.8 +/- 7.9%, p = 0.03) coronary arteries, but diagonal artery occlusion caused no significant change in right ventricular ejection fraction. Occlusion of the right coronary artery proximal (but not distal) to the acute marginal branch caused a significant decrease in right ventricular ejection fraction (from 42.6 +/- 4.7% to 35.7 +/- 7.2%, p < 0.01). Although occlusion of the left anterior descending, left circumflex and proximal right coronary arteries all caused significant deterioration in regional right ventricular function, only proximal right coronary occlusion caused right ventricular dilation (p < 0.005).

CONCLUSIONS

Significant impairment of right ventricular function occurs during transient occlusion of the left anterior descending, left circumflex and proximal right coronary arteries, but only occlusion of the latter causes acute right ventricular dilation, probably as a result of ischemia.

Doppler assessment of left ventricular diastolic function: a review

Two-dimensional echocardiography provides valuable information for the assessment of left ventricular function. Traditionally, evaluation has focused on determination of systolic performance. However, recent investigations indicate diastolic dysfunction may also contribute to symptoms of congestive heart failure in many patients despite normal systolic function. Pulsed Doppler echocardiography complements two-dimensional imaging for assessment of left ventricular filling properties that are often altered in the setting of diastolic dysfunction. The concept of diastolic function and recognition of abnormal filling patterns detected by pulsed Doppler echocardiography are reviewed.

Analysis of the signal-averaged P-wave duration in patients with percutaneous coronary angioplasty-induced myocardial ischemia

To assess the impact of angioplasty-induced myocardial ischemia on the duration of the surface P wave, patients undergoing elective angioplasty of isolated lesion in the left anterior descending, circumflex or right coronary arteries were monitored with a 3-channel electrocardiographic Holter system. The leads used were modified bipolar chest leads V5, aVF and V2 (CM-V5, CS-aVF and CM-V2). After echocardiographic signal-averaging, the earliest onset and the latest offset of the P wave were identified in all of the above time-aligned signal-averaged leads, and the composite maximal P duration was measured under 10 x magnification. The maximal ST-segment shift during balloon inflation was also measured in all of the above leads at 60 ms after the J point. In the study group comprising 47 patients, the mean signal-averaged P-wave duration was 125.0 +/- 16 ms at baseline versus 130.0 +/- 15 ms during balloon inflation, p less than 0.005. In the left anterior descending coronary artery group (n = 23), the mean signal-averaged P-wave duration was 122.4 +/- 17 ms and 131.3 +/- 16 ms during balloon inflation, p less than 0.005). In the group with a right coronary artery lesion (n = 18), the values were 127.3 +/- 14 ms and 128.4 +/- 13 ms respectively (p = not significant). Significant increases in the P-wave duration were found to occur in groups both with (n = 34) and without (n = 13) ST-segment shift greater than or equal to 1 mm (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of myocardial reperfusion injury by sulfhydryl-containing angiotensin converting enzyme inhibitors

Recent studies have suggested the beneficial effects of angiotensin converting enzyme (ACE) inhibitors against myocardial ischemic-reperfusion injury. This study was designed to compare the cardioprotective effects of two sulfhydryl ACE inhibitors, captopril and zofenopril, with those of a nonsulfhydryl ACE inhibitor, fosinopril. The efficacy of these ACE inhibitors to scavenge oxygen radicals in vitro were also examined. Isolated rat hearts perfused by the Langendorff technique were preperfused in the presence or absence of ACE inhibitors (50 microns for 15 minutes, and the hearts were then subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion. Zofenopril and captopril, but not fosinopril, improved postischemic left ventricular functions and reduced myocardial cellular injury, as evidenced by improved recovery of the first derivative of left ventricular pressure development and reduced creatine kinase release compared with control (p less than .05). Coronary flow was significantly increased by captopril and zofenopril only. The same two drugs also inhibited the enhanced lipid peroxidation during reperfusion. Although significant differences were not noticed in the postischemic myocardial membrane phospholipid composition, captopril and zofenopril reduced nonesterified fatty acid contents, including palmitic, linoleic, oleic, and arachidonic acids. In vitro studies demonstrated that captopril and zofenopril were able to scavenge hydroxyl radicals. These results indicate that among three ACE inhibitors, two sulfhydryl-containing drugs, captopril and zofenopril, possess cardioprotective as well as free-radical scavenging abilities. Attenuation of phospholipid degradation and lipid peroxidation may be contributory to the protective effects observed in this study.

Clinical and experimental aspects of myocardial stunning

Although the mechanisms involved in stunning remain incompletely defined, it appears that intracellular calcium overload, sarcoplasmic reticulum dysfunction, and the generation of OFR are important components of post-ischemic myocyte dysfunction. It is likely that a variety of mechanisms, some possibly remaining to be elucidated, are operative in the pathogenesis of stunning, and that the contribution of a particular process may be influenced by the model and the method of inducing ischemia. Myocardial stunning has been shown to be prevalent in patients with diverse cardiac diseases. Small clinical trials have suggested that electrocardiography, echocardiography, and radionuclide imaging techniques may be useful in identifying patients with stunned myocardium. In patients with depressed cardiac performance due to stunning, therapy with inotropic agents may recruit the viable but injured myocardium to contract and improve cardiac output in the short term. An important issue that will be addressed over the next decade is whether aggressive therapy aimed at reducing myocardial stunning in stable patients should be attempted. Some authorities have suggested that stunning may represent an adaptive response to limit reperfusion injury, and that interfering with this response may not be beneficial in the long term. Further investigation into the cellular and molecular basis of ischemic injury should provide insight into these and other important aspects of myocardial stunning. Methods of attenuating postischemic ventricular dysfunction that appear convincing in the research laboratory may not translate to clinical benefit when applied to humans.

The effect of exercise-induced myocardial ischemia on postischemic left ventricular diastolic filling

To determine whether exercise-induced ischemia impairs left ventricular diastolic filling in the postischemic period in humans, 101 men (mean age 57 +/- 10 years) were studied before and 2 h after a symptom-limited thallium-201 tomographic treadmill with pulsed Doppler echocardiography of mitral valve inflow. In the postischemic period 2 h after exercise, diastolic filling was significantly impaired in the ischemia group (reversible thallium defect; n = 24) as reflected by a decrease in the peak early filling velocity (44.5 +/- 10.1 to 39.9 +/- 9.9 cm/s, p less than 0.01), peak early to atrial filling velocity ratio (0.91 +/- 0.27 to 0.76 +/- 0.25, p less than 0.001), and deceleration rate of early filling (281 +/- 104 to 245 +/- 86 cm/s2, p less than 0.01). Similar alterations in the postischemic period occurred in the myocardial infarction-ischemia group (partially reversible defect; n = 28) as seen by a decrease in the peak early filling velocity (47.6 +/- 11.6 to 41.8 +/- 12.0 cm/s, p less than 0.001), peak early to atrial filling velocity ratio (0.84 +/- 0.21 to 0.68 +/- 0.18, p less than 0.001), and early time-velocity integral (7.06 +/- 1.78 to 5.64 +/- 2.07 cm, p less than 0.001). In the control group (no defects; n = 33) and myocardial infarction group (fixed defect; n = 16), diastolic filling was unchanged in the postexercise period. Heart rate and blood pressure were unchanged post-exercise in all groups. Exercise-induced ischemia impairs diastolic filling in the postischemic period in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of left ventricular performance during transient coronary occlusion at various anatomic sites in humans: a study using tantalum-178 and a multiwire gamma camera

To study the functional significance of transient coronary occlusion on systolic and diastolic left ventricular function relative to the anatomic site of occlusion, first-pass radionuclide angiography with a mobile multiwire gamma camera using tantalum-178 (dose activity less than or equal to 84 mCi/elution) was performed in 46 patients undergoing balloon coronary angioplasty. First-pass images were acquired immediately before angioplasty and during the last 30 s of a 60-s balloon inflation in 23 left anterior descending arteries, 18 right coronary arteries, 8 circumflex arteries and 3 diagonal coronary arteries. Occlusion of the left anterior descending artery resulted in significant decreases in left ventricular ejection fraction (54.6 +/- 12.7% to 32.3 +/- 10.6%, p = 0.0001) and peak filling rate (2.48 +/- 0.68 to 1.75 +/- 0.64 end-diastolic volumes/s, p = 0.0001), accompanied by severe abnormalities in regional function and left ventricular dilation. Right coronary artery occlusion caused inferior hypokinesia, but did not significantly change left ventricular ejection fraction (48.5 +/- 12.4% vs. 45.8 +/- 12.5%, p = NS) or peak filling rate (2.05 +/- 0.81 vs. 2.09 +/- 0.81 end-diastolic volumes/s, p = NS). Circumflex artery occlusion resulted in mild wall motion deterioration and a borderline decrease in ejection fraction (54.7 +/- 11.4% to 50.5 +/- 12%, p = 0.057). Diagonal artery occlusion did not cause significant changes in left ventricular ejection fraction or filling rate. The decrease in left ventricular ejection fraction during coronary occlusion was 9 +/- 25% and 27 +/- 22%, respectively, in those arteries with and without collateral supply (p = 0.052). These data provide strong evidence for the critical importance of the left anterior descending artery and the secondary role of the other coronary arteries in maintaining global systolic and diastolic left ventricular function and suggest a protective role of collateral vessels during coronary occlusion.

Clinical relevance of myocardial "stunning"

Experimental studies have demonstrated that myocardium reperfused after reversible ischemia exhibits prolonged depression of contractile function ("stunning"). Despite the multiplicity of clinical situations in which myocardial stunning would be expected to occur, investigation of this phenomenon in humans has been hindered by several major problems, including the limited accuracy of the methods available to measure regional left ventricular function, the inability to quantify regional myocardial blood flow during acute ischemia, the difficulty in establishing with certainty, the beginning and end of an ischemic episode, and the uncontrolled influence of variables (such as preload, afterload, adrenergic tone, and inotropic therapy) that have a major impact on postischemic dysfunction. The main problem is to discern whether a reversible defect of contractility is caused by stunning, silent ischemia, or hibernation (i.e., chronic ischemia). This differential diagnosis requires the simultaneous measurement of regional myocardial function and flow, which thus far has not been generally possible. Despite these limitations, however, numerous clinical observations suggest that stunning does occur in various settings in which the myocardium is exposed to transient ischemia, including coronary angioplasty, exercise-induced angina, angina at rest (unstable or variant), acute myocardial infarction with early reperfusion, open-heart surgery, and cardiac transplantation. Recognition of this entity is important, amongst other reasons, because it is likely to cause significant morbidity and because it is potentially correctable with inotropic therapy or even preventable with antioxidant therapy. In addition, the appreciation of the phenomenon of myocardial stunning should allow the clinician to assess the efficacy of reperfusion therapy with greater accuracy and to recognize that patients should not be denied mechanical revascularization solely because of an abnormal left ventricular wall motion. Perhaps the most intriguing clinical implication of the concept of myocardial stunning is the possibility that in patients who exhibit frequent episodes of ischemia in the same territory, the myocardium may not be able to fully recover between episodes and thus may remain reversibly depressed for prolonged periods of time, or even chronically, which could account for some cases of "ischemic cardiomyopathy." Our understanding of myocardial stunning in humans is still relatively crude and will not significantly improve until studies are performed that measure simultaneously regional myocardial perfusion and function (so that stunning can be differentiated from silent ischemia and hibernation). Future important areas of research should also include the elucidation of whether stunning can become chronic and the evaluation of therapies (such as antioxidant treatments) designed to prevent this contractile abnormality.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of adenosine in the treatment of myocardial stunning

Adenosine is an endogenous nucleoside produced from the breakdown of adenosine triphosphate (ATP) that possesses a number of complex cellular and metabolic effects that could ameliorate postischemic contractile dysfunction (myocardial stunning). Potential mechanisms include the repletion of high-energy phosphate stores, reduced myocardial oxygen consumption, a decrease in oxygen-derived free radicals, restoration of calcium homeostasis, and an increase in regional myocardial blood flow. Experimental studies have shown that adenosine can reduce myocardial stunning with or without a concomitant increase in the total myocardial ATP stores. Adenosine may be a useful pharmacologic strategy in the prevention and treatment of ventricular dysfunction following episodes of regional or global ischemia, although further studies are needed to clarify the precise cellular mechanisms involved.

Congestive heart failure in coronary artery disease

Congestive heart failure (CHF) affects approximately 1% of the United States population and its incidence continues to increase. Next to hypertension, coronary artery disease (CAD) is the second most frequent cause of CHF. Important distinction should be made between systolic dysfunction and diastolic dysfunction in CAD. The diagnostic and therapeutic challenges posed by both have stimulated much investigation into the pathophysiologic mechanisms involved and have led to innovative pharmacologic interventions to forestall progression of the disease. The challenge in the 1990s is prevention. In the meantime, results of completed and ongoing randomized controlled trials will determine the most effective forms of therapy, which will not only improve symptoms but also hopefully extend survival.

Effects of an increase in intracellular free [Mg2+] after myocardial stunning on sarcoplasmic reticulum Ca2+ transport

BACKGROUND

Myocardial stunning has been associated with a greater than twofold increase in intracellular free [Mg2+] from 0.6 to 1.5 mM. The effect of this increase in free [Mg2+] on the function of the sarcoplasmic reticulum (SR) Ca2+ pump was assessed in SR isolated from Langendorff perfused, isovolumic rabbit hearts after 15 minutes of global ischemia.

METHODS AND RESULTS

Our results indicate that myocardial stunning results in a shift in the Ca2+ sensitivity of oxalate-supported, Ca2+ transport over the entire range of free [Ca2+] associated with the cardiac cycle. Using 0.6 mM free Mg2+ as control, maximal rates of Ca2+ transport occurred at 1 microM free Ca2+ (control, 519 +/- 32; stunned, 337 +/- 37 nmol Ca2+.min-1.mg-1). At 0.56 microM free Ca2+, SR Ca2+ transport was reduced from a control of 351 +/- 49 to 263 +/- 12 nmol Ca2+.min-1.mg-1 at 0.6 mM free [Mg2+]. Moreover, an increase in the free [Mg2+] from 0.6 to 1.5 mM results in a greater shift in the Ca2+ activation curve with no change in the level of maximal activation. Ca2+ transport at 0.56 microM free Ca2+ was shifted in the stunned SR from 263 +/- 12 to 138 +/- 29 nmol Ca2+.min-1.mg-1 at 0.6 and 1.5 mM free Mg2+, respectively.

CONCLUSIONS

These results indicate that an increase in free [Mg2+] after stunning in combination with the inherent defect in the SR Ca2+ ATPase may reduce the ability of the cell to regulate Ca2+ to a greater extent than previously observed. This impairment in Ca2+ regulatory function may contribute directly to the increase in diastolic tone and indirectly to the reduced systolic function characteristic of the stunned myocardium.

Comparison of chest pain, electrocardiographic changes and thallium-201 scintigraphy during varying exercise intensities in men with stable angina pectoris

This study was performed to evaluate the presence of angina pectoris, electrocardiographic changes and reversible thallium-201 defects resulting from 2 different levels of exercise in 19 patients with known coronary artery disease and evidence of exercise-induced ischemia. The exercise protocols consisted of a symptom-limited incremental exercise test (Bruce protocol) followed within 3 to 14 days by a submaximal, steady-state exercise test performed at 70% of the maximal heart rate achieved during the Bruce protocol. The presence and time of onset of angina and electrocardiographic changes (greater than or equal to 0.1 mV ST-segment depression) as well as oxygen uptake, exercise duration and pressure-rate product were recorded. Thallium-201 (2.5 to 3.0 mCi) was injected during the last minute of exercise during both protocols, and the images were analyzed using both computer-assisted quantitation and visual interpretations. Incremental exercise resulted in anginal symptoms in 84% of patients, and electrocardiographic changes and reversible thallium-201 defects in all patients. In contrast, submaximal exercise produced anginal symptoms in only 26% (p less than 0.01) and electrocardiographic changes in only 47% (p less than 0.05), but resulted in thallium-201 defects in 89% of patients (p = not significant). The locations of the thallium-201 defects, when present, were not different between the 2 exercise protocols. These findings confirm the sequence of the ischemic cascade using 2 levels of exercise and demonstrate that the cascade theory is applicable during varying ischemic intensities in the same patient.

The stunned and hibernating myocardium: a brief review

DEFINITIONS

Stunned myocardium is viable myocardium salvaged by coronary reperfusion that exhibits prolonged postischemic dysfunction after reperfusion. Hibernating myocardium is ischemic myocardium supplied by a narrowed coronary artery in which ischemic cells remain viable but contraction is chronically depressed.

CLINICAL EVIDENCE

Stunned myocardium has been identified in the following patient groups: (1) thrombolysis or percutaneous transluminal coronary angiography (PTCA) in patients with acute evolving infarction; (2) unstable angina; (3) exercise-induced angina; (4) coronary artery spasm; (5) platelet aggregation or transient thrombosis of a coronary artery; (6) PTCA for chronic myocardial ischemia; and (7) immediately following coronary artery bypass graft (CABG). Evidence of hibernating myocardium (LV dysfunction) is found in the patient with severe coronary artery stenosis, even in asymptomatic patients at rest. Stunned myocardium returns to normal after a prolonged period of time (hours to weeks). Hibernating myocardium returns to normal function rather quickly if the cause is removed.

DIFFERENTIATION

Stunned myocardium can be differentiated from hibernating myocardium by three clinical parameters, namely, LV wall motion, myocardial perfusion, and myocardial metabolism. Stunned myocardium has abnormal wall motion that tends to normalize in response to inotropes and postextrasystolic potentiation. Perfusion is adequate and metabolism is also adequate. Hibernating myocardium also has abnormal wall motion, which normalizes after nitrates, inotropes, post extrasystolic potentiation (PESP), PTCA, or CABG. Myocardial perfusion is reduced but can be reversed with PTCA or CABG and metabolism is adequate.

Left ventricular function during transient coronary occlusion: digital subtraction left ventriculograms during coronary angioplasty

The impact of transient myocardial ischemia on left ventricular function was examined by digital subtraction left ventricular angiography. Contrast medium was injected into the right pulmonary artery before, at 60 seconds of balloon inflation, and 10 minutes after balloon deflation. A total of 69 patients completed the study. In 52 patients, the left anterior descending artery (LAD) was involved, and in 17, the right coronary artery (RCA) was the focus. Ejection fraction (EF) declined by balloon inflation and returned to baseline value after deflation of the balloon. There was tendency toward a lower EF and wider akinetic area for LAD dilatation. The linear correlation between resting EF and EF during balloon inflation suggested that the effect of momentary coronary occlusion on left ventricular function appears to be additive to pre-existing left ventricular dysfunction, and resting ejection fraction is an important parameter for estimating the degree of diminished left ventricular function during myocardial ischemia.

Stunned left ventricular myocardium after exercise treadmill testing in coronary artery disease

Myocardial stunning (postischemic ventricular dysfunction) occurs in dogs after coronary stenosis following treadmill exercise. Less data are available in humans regarding development of stunned myocardium after exercise. Regional wall motion changes were evaluated in 22 patients with known coronary artery disease using 2-dimensional echocardiography and exercise treadmill testing. Wall motion was scored as 1 = normal, 2 = hypokinetic, 3 = akinetic, 4 = dyskinetic. At least 1 left ventricular segment with normal resting function developed an increase in wall motion score at 15 or 30 minutes compared with values at rest. The wall motion score in the midportion of the ventricular septum increased from 1.0 at rest to 1.6 (p less than 0.004) at 30 minutes after exercise; the basal inferior wall score worsened from 1.0 at rest to 1.9 (p less than 0.01) at 30 minutes after exercise. Coronary angiographic data in these patients revealed that left anterior descending narrowing correlated best with left ventricular septal wall motion abnormalities, whereas right coronary artery and circumflex narrowing best correlated with inferior and posterior wall motion abnormalities. Eight normal adult volunteers with no history of myocardial ischemia also underwent 2-dimensional echocardiography and exercise testing. No wall motion abnormalities were observed at any time after exercise. The present study suggests that in patients with coronary artery disease, exercise treadmill testing may induce regional wall motion abnormalities of the left ventricle that persist greater than or equal to 30 minutes after exercise, an observation consistent with the phenomenon of stunned myocardium.

Assessment of the extent of jeopardized myocardium during acute coronary artery occlusion followed by reperfusion in man using technetium-99m isonitrile imaging

We tested the feasibility of technetium-99m methoxyisobutyl isonitrile (Tc-MIBI) imaging for delineating jeopardized myocardium during acute coronary occlusion and reperfusion in man. This new perfusion agent was injected in 25 patients during elective percutaneous transluminal coronary angioplasty (PTCA) of a single-vessel left anterior descending (LAD) coronary artery stenosis. Distinct perfusion defects were present on "occlusion" images but not on "open vessel" images obtained 20 to 24 hours later in 21 patients (84%). The extent and severity of perfusion defects were significantly smaller in patients with distal versus proximal LAD occlusions (3.4 +/- 1.2 versus 5.2 +/- 1.5 segments; p less than 0.001). The only factor that was significantly related to the presence or absence of such "ischemic" perfusion defects was the absence or presence of visible collateral vessels to the LAD (p less than 0.03). The site of occlusion, presence of wall motion abnormalities, or occlusion time did not influence the results significantly. Thus the myocardial area at risk could be visualized and quantitated by Tc-MIBI imaging even after occlusion times as short as 15 seconds, but functioning collateral vessels are capable of protecting jeopardized myocardium in this setting.

Comparative effects of pacing-induced and balloon coronary occlusion ischemia on left ventricular diastolic function in man

BACKGROUND

Effects of pacing-induced and coronary occlusion myocardial ischemia on left ventricular (LV) function have been compared only in anesthetized dogs. Diastolic properties of the same LV anterior wall segment were therefore compared in 12 patients with single-vessel proximal left anterior descending coronary artery stenosis at rest, immediately after 7 +/- 1.2 minutes of pacing, and at the end of a 1-minute balloon occlusion of coronary angioplasty (CO).

METHODS AND RESULTS

Shifts of the diastolic LV pressure-length relation, derived from simultaneous tip-micromanometer LV pressure recordings and digital subtraction LV angiograms, were used as an index of regional diastolic LV distensibility of the anterior wall segment. Immediately after pacing, LV end-diastolic pressure rose from 13.5 +/- 3.5 to 23.8 +/- 7.0 mm Hg (p less than 0.01 versus at rest) without a significant change of the LV end-diastolic volume index (83.1 +/- 18.9 versus 88.4 +/- 16.5 ml/m2), percentage systolic shortening (%SS) of the ischemic segment fell from 40.1 +/- 10.6% to 25.2 +/- 8.6% (p less than 0.01), and the diastolic LV pressure-radial length (P-RL) plot of the ischemic segment was shifted upward by 7.1 +/- 5.0 mm Hg for portions of the plot that overlapped with the diastolic LV P-RL plot at rest. At the end of CO, LV end-diastolic pressure rose to 20.8 +/- 7.8 mm Hg (p less than 0.01 versus at rest) and the LV end-diastolic volume index rose to 95.6 +/- 16.3 ml/m2 (p less than 0.05 versus at rest, p less than 0.05 versus after pacing). Ejection fraction and %SS of the ischemic segment fell respectively from 76.6 +/- 6.8% to 46.6 +/- 11.4% (p less than 0.01 versus at rest, p less than 0.01 versus after pacing) and from 40.1 +/- 10.6% to 6.4 +/- 8.6% (p less than 0.01 versus at rest, p less than 0.01 versus after pacing). The diastolic LV P-RL plot of the ischemic segment was shifted upward by 3.1 +/- 2.3 mm Hg for portions of the plot that overlapped with the diastolic LV P-RL plot at rest. This upward shift at the end of CO was significantly smaller (p less than 0.05) than that immediately after pacing. At the end of CO, a correlation (p less than 0.03) was observed for the ischemic segment between %SS and upward shift of the diastolic LV P-RL plot.

CONCLUSIONS

The upward shift of the diastolic LV P-RL plot, which was used as an index of decreased regional diastolic LV distensibility, was larger immediately after pacing than at the end of CO. Persistent systolic shortening of ischemic myocardium seems to be a prerequisite for a decrease in diastolic distensibility of the ischemic segment because of the higher %SS of the ischemic segment immediately after pacing, and because of the correlation at the end of CO between the upward shift of the diastolic LV P-RL plot and %SS of the ischemic segment.

Effects of hemoperfusion during percutaneous transluminal coronary angioplasty on left ventricular function

The effect of autologous blood perfusion, delivered through an angiographic power injector, on alleviating left ventricular (LV) hemodynamic deterioration during percutaneous transluminal coronary angioplasty (PTCA) was examined. LV systolic and diastolic pressures, LV peak positive and peak negative first derivative of LV pressure (dP/dt), and ST-segment shift were recorded in 9 patients with and without hemoperfusion. Hemoperfusion resulted in an improved LV hemodynamic profile during balloon occlusion, as reflected in LV systolic pressure (127 +/- 14 vs 120 +/- 15 mm Hg, p = 0.01), LV end-diastolic pressure (17 +/- 14 vs 25 +/- 6 mm Hg, p less than 0.001), peak positive (1,237 +/- 240 vs 1,149 +/- 225 mm Hg/s, p less than 0.05) and peak negative (1,666 +/- 357 vs 1,485 +/- 385 mm Hg/s, p = 0.003) dP/dt. Hemoperfusion provides substantial protection for significant LV dysfunction induced by conventional PTCA in 1-vessel angioplasty and is a feasible option to protect against potential cardiovascular collapse in high-risk PTCA.

Symptom-limited exercise testing causes sustained diastolic dysfunction in patients with coronary disease and low effort tolerance

Exercise stress testing is routinely used for the noninvasive assessment of coronary artery disease and is considered a safe procedure. However, the provocation of severe ischemia might potentially cause delayed recovery of myocardial function. To investigate the possibility that maximal exercise testing could induce prolonged impairment of left ventricular function, 15 patients with angiographically proved coronary disease and 9 age-matched control subjects with atypical chest pain and normal coronary arteries were studied. Radionuclide ventriculography was performed at rest, at peak exercise, during recovery and 2 and 7 days after exercise. Ejection fraction, peak filling and peak emptying rates and left ventricular wall motion were analyzed. All control subjects had a normal exercise test at maximal work loads and improved left ventricular function on exercise. Patients developed 1 mm ST depression at 217 +/- 161 s at a work load of 70 +/- 30 W and a rate-pressure product of 18,530 +/- 4,465 mm Hg x beats/min. Although exercise was discontinued when angina or equivalent symptoms occurred, in all patients diagnostic ST depression (greater than or equal to 1 mm) developed much earlier than symptoms. Predictably, at peak exercise patients showed a decrease in ejection fraction and peak emptying and filling rates. Ejection fraction and peak emptying rate normalized within the recovery period, whereas peak filling rate remained depressed throughout recovery (p less than 0.002) and was still reduced 2 days after exercise (p less than 0.02). In conclusion, in patients with severe impairement of coronary flow reserve, maximal exercise may cause sustained impairement of diastolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical efficacy of PTCA and identification of restenosis: evaluation by serial body surface potential mapping

We used serial body surface potential mapping (BSPM) with the departure map technique to evaluate the clinical efficacy of percutaneous transluminal coronary angioplasty (PTCA) in various pathophysiologic stages of coronary artery disease, and to detect restenosis. The BSPM was performed prior to, 1 week after, and 1 month after PTCA. A follow-up coronary angiography was performed 3 to 6 months after PTCA, and BSPM was also performed at the same time. The results of BSPM were compared with those of thallium-201 single-photon emission computed tomography (Tl-201 SPECT) and radionuclide ventriculography. After PTCA, BSPM showed a significant reduction in the departure area, the Tl-201 SPECT also showed a significant reduction in the extent and severity scores, and the left ventricular ejection fraction improved significantly. In the cases with restenosis, the departure area, which had decreased in size after PTCA, showed an increase in size. After successful re-PTCA, the size of the departure area again became smaller. We concluded that BSPM, which is a simple, noninvasive, and inexpensive method, is useful in the evaluation of the clinical efficacy of PTCA and in the detection of restenosis after successful PTCA.

The effects of pretreatment with nitroglycerin on ischemic left ventricular dysfunction during coronary angioplasty

To evaluate the degree to which nitroglycerin reduces myocardial ischemia and dysfunction induced by transient coronary occlusion, 19 patients were studied during coronary angioplasty of the left anterior descending coronary artery. After a control occlusion of 60 seconds, 0.2 mg nitroglycerin was administered intravenously and the occlusion was repeated for 60 seconds. Before and during the occlusion period, pulmonary capillary wedge pressure was measured, the intracoronary ECG was recorded, and ventricular volumes, ejection fraction, and regional systolic shortening were obtained by digital subtraction angiography. Nitroglycerin caused a significant fall in pulmonary capillary wedge pressure before (10 vs. 7 mmHg) and at 60 seconds occlusion (18 vs. 14 mmHg), but did not significantly delay the rise in wedge pressure (37 vs. 44 seconds). End-systolic left ventricular volume at 60 seconds of occlusion was reduced by nitroglycerin (77 vs. 68 ml), whereas regional shortening of the ischemic segments remained unchanged (22 vs. 23%). Nitroglycerin did not delay the onset of ischemic ST-segment elevation (14 vs. 14 seconds) and had no effect on the changes of ST elevation in the intracoronary ECG (1.9 vs. 1.9 mV). These findings suggest that intravenous nitroglycerin reduces filling pressure and slightly improves left ventricular global function during acute coronary occlusion. Nitroglycerin, however, has little effect on ischemia-induced regional dysfunction and on ST-segment elevation in the intracoronary ECG.

Left ventricular passive diastolic properties in chronic mitral regurgitation

BACKGROUND

In chronic mitral regurgitation, the myocardium responds to the increased filling volume by geometric alteration and eccentric hypertrophy. This study was designed to evaluate the effects of a pure volume overload on left ventricular diastolic chamber and myocardial properties and to assess the relation of passive diastolic function to systolic ejection performance.

METHODS AND RESULTS

By use of simultaneous cineangiography and left ventricular micromanometry, left ventricular passive diastolic stiffness was evaluated in nine normal controls (group 1), 14 patients with chronic mitral regurgitation and a normal ejection fraction (greater than or equal to 57%, group 2), and 13 patients with mitral regurgitation and a reduced ejection fraction (less than 57%, group 3). Passive diastolic function was evaluated by using a three-constant elastic model. Left ventricular chamber properties were represented by the relation of pressure to volume; myocardial properties were evaluated by relating myocardial midwall stress to midwall strain. The constant of left ventricular chamber stiffness was decreased in group 2 compared with controls (p less than 0.05) but it was normal in group 3. The constant of myocardial stiffness was increased in group 3 compared with groups 1 and 2 (p less than 0.01). Among patients with mitral regurgitation, there was a significant inverse relation between ejection fraction and the constant of myocardial stiffness (r = -0.83).

CONCLUSIONS

The chronic adaptation to volume overload in chronic mitral regurgitation tends to decrease left ventricular chamber stiffness. Patients with mitral regurgitation and a depressed ejection fraction demonstrated diastolic myocardial dysfunction. Compromised diastolic function in patients with chronic mitral regurgitation and reduced systolic performance may contribute to the clinical manifestations of congestive heart failure.

Improvement of systolic and diastolic left ventricular wall motion by serial echocardiograms in selected patients treated for unstable angina

The purpose of the study was to evaluate the effect of antiischemic treatment on left ventricular function in selected patients with unstable angina pectoris that was due to severe proximal left anterior descending coronary artery narrowing and to identify subgroups liable to an adverse outcome (mean term 2.7 years). Effect of antiischemic treatment on systolic and diastolic left ventricular wall motion was studied in 35 patients who had unstable angina pectoris and an electrocardiogram that indicated severe proximal left anterior descending coronary artery narrowing. Treatment consisted of either a revascularization procedure (17 patients) or antianginal drug therapy (18 patients). All patients underwent a two-dimensional echocardiographic study within 48 hours (mean 20 hours) of entry into the study. This study semiquantitatively analyzed systolic performance of the ischemia-related segments by calculation of a total wall motion score. In 16 patients this investigation was combined with a continuous detailed recording of only the apical interventricular septal wall motion. This detailed study included measurements for regional function by providing a typification of the pattern of systolic and early diastolic excursion of the endocardial border of the apical interventricular septum. A repeat ultrasonic study was performed at least 1 month (median 2 months, 7 days) after admission. Results of the systolic wall motion analyses of all 35 patients showed, in both treatment groups, a significant improvement in systolic wall motion of the anterior and apical segments (mean total wall motion score at early study vs late study: revascularization, 6.9 vs 2.2 and medical therapy, 4.6 vs 1.0).(ABSTRACT TRUNCATED AT 250 WORDS)

Load dependence of left ventricular diastolic pressure-volume relations during short-term coronary artery occlusion

We evaluated the effect of altered loading conditions on left ventricular (LV) diastolic pressure-volume relations during acute coronary artery occlusion that was produced by inflation of an intracoronary balloon. Open-chest anesthetized dogs (n = 18) were instrumented so that LV pressure (micromanometer) and LV volume (conductance) could be measured without disturbing the pericardium. The effects of brief periods of occlusion (1-2 minutes) were assessed under steady-state conditions before and after dextran infusion with the pericardium present and absent and during vena caval occlusion. Under steady-state conditions before dextran infusion with the pericardium removed, at an LV end-diastolic pressure (EDP) of 8.4 +/- 1.4 mm Hg, occlusion resulted in a rightward shift in the diastolic portion of the LV pressure-volume loop (delta LVEDP, 2.7 +/- 2.3 mm Hg; delta LVEDV, 6.3 +/- 4.7 ml, both p less than 0.05 versus control). After dextran infusion (LVEDP, 20.9 +/- 6.0 mm Hg), occlusion resulted in a rightward and upward shift in the diastolic portion of the LV pressure-volume loop (delta LVEDP, 5.8 +/- 4.4 mm Hg; delta LVEDV, 4.2 +/- 3.0 ml, both p less than 0.05 versus control). At low cardiac volumes before dextran infusion, the intact pericardium did not affect the response to occlusion. By contrast, after dextran infusion in the presence of an intact pericardium, LVEDP significantly increased (delta, 6.4 +/- 3.6 mm Hg, p less than 0.05) but LVDEV did not (delta, 0.7 +/- 1.5 ml, p = NS). There was a parallel upward shift in the diastolic portion of the LV pressure-volume loop that was eliminated by removal of the pericardium. Thus, the change in LV diastolic pressure and volume during occlusion varied and depended on the baseline cardiac volume and presence of the pericardium. Before dextran infusion with the pericardium present and absent, coronary artery occlusion did not alter the LV diastolic chamber stiffness parameter, which was calculated from the diastolic interval of an averaged steady-state beat (0.040 +/- 0.019 versus 0.036 +/- 0.015 mm Hg/ml, p = NS). After dextran infusion with the pericardium present and absent, coronary artery occlusion increased the LV diastolic chamber stiffness parameter (0.057 +/- 0.034 and 0.074 +/- 0.034 mm Hg/ml, both p less than 0.05 versus controls, respectively). Vena caval occlusion eliminated the shifts in the diastolic portion of the LV pressure-volume loop with the pericardium present and absent.(ABSTRACT TRUNCATED AT 400 WORDS)

Does intracoronary infusion of Fluosol-DA 20% prevent left ventricular diastolic dysfunction during coronary balloon angioplasty?

Distal intracoronary infusion of the perfluorochemical Fluosol-DA 20% has been shown to prevent systolic dysfunction during coronary artery balloon occlusion in coronary angioplasty. To assess its effect on global diastolic dysfunction, a randomized, single-blind, crossover protocol comparing intracoronary infusion of Fluosol or no infusion (control) was performed during 60 s balloon inflations in 10 patients (mean age 67 years) undergoing coronary angioplasty. Assessment of global systolic and diastolic function was obtained with high fidelity micromanometer measurements of left ventricular pressure. Eighteen pairs of balloon inflations (Fluosol versus control) were analyzed. Patients reported significantly less severe chest pain during inflations accompanied by Fluosol compared with control. However, during coronary balloon occlusion, no significant differences in the changes from baseline values were observed between Fluosol and control with regard to ventricular relaxation, including the time constant of early ventricular relaxation (tau) and maximal rate of fall in left ventricular pressure (maximal negative dP/dt). No differences between Fluosol and control were observed in terms of the increase in end-diastolic pressure or minimal diastolic pressure during balloon inflation. Mean systolic pressure decrease from baseline values was greater during control than during Fluosol inflations (-9.0 +/- 3.3 mm Hg, p = 0.013), but no significant difference was observed in the change in maximal rate of rise in left ventricular pressure (maximal positive dP/dt). These results suggest that Fluosol does not preserve global left ventricular diastolic function during coronary balloon occlusion, possibly because of its limited oxygen delivery capability relative to arterial blood.

Reversal of segmental hypokinesis by coronary angioplasty in patients with unstable angina, persistent T wave inversion, and left anterior descending coronary artery stenosis. Additional evidence for myocardial stunning in humans

To evaluate the significance of persistent negative T waves during severe ischemia, we prospectively studied 62 patients admitted for unstable angina without evidence of recent or ongoing myocardial infarction. A critical stenosis on the left anterior descending coronary artery (LAD), considered as the culprit lesion, was successfully treated by percutaneous transluminal coronary angioplasty (PTCA). The patients were divided into two groups according to the admission electrocardiogram: T NEG group (n = 32) had persistent negative T waves, and the T POS group (n = 30) had normal positive T waves on precordial leads. The two groups had similar baseline clinical, hemodynamic, and angiographic characteristics. All patients underwent a complete clinical and angiographic evaluation (coronary arteriography and left ventriculography) before undergoing PTCA and 8 +/- 3 months later. Left ventricular anterior wall motion was evaluated by the percent shortening of three areas (S1, S2, and S3) considered as LAD-related segments on left ventriculograms. Before PTCA, there was no significant difference in global ejection fraction between the two groups despite a significant depression in anterior mean percent area shortening in the T NEG compared with the T POS group (S1, 44 versus 54, p less than 0.01; S2, 39 versus 48, p less than 0.01; S3, 44 versus 50, NS). At repeated angiography, the anterior mean percent area shortening improved significantly in the T NEG group (S1, from 44 to 61, p less than 0.001; S2, from 39 to 58, p less than 0.001; S3, from 44 to 61, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of pretreatment with intracoronary nifedipine on myocardial ischemia and dysfunction

To assess whether pretreatment with intracoronary nifedipine protects the myocardium against acute ischemia induced by coronary occlusion, 18 patients were studied during coronary angioplasty of the left anterior coronary artery. After a control occlusion of 60 seconds, 0.1 mg nifedipine was injected and occlusion was repeated for 60 seconds. Before and during the occlusion period, pulmonary capillary pressure was measured and the intracoronary epicardial ECG was recorded. After intracoronary administration of nifedipine, the onset of the rise in diastolic filling pressure was delayed from 23 to 38 seconds (p less than 0.01) and the changes at 60 seconds of occlusion were reduced from 14 to 11 mmHg (p less than 0.05). Nifedipine delayed the appearance of ischemic ST-segment elevation in the intracoronary ECG from 11 to 21 seconds (p less than 0.01) and diminished the changes at 60 seconds of occlusion from 1.8 to 1.2 mV (p less than 0.05). These findings suggest that pretreatment with intracoronary nifedipine protects the myocardium against some of the mechanical and electrocardiographic consequences of regional ischemia during acute coronary occlusion.

Granulocyte activation after coronary angioplasty in humans

To determine whether percutaneous transluminal coronary angioplasty (PTCA) would lead to neutrophil activation with subsequent discharge of proteolytic enzymes, like elastase, and oxygen free radicals, like superoxide anion, blood samples were taken from the coronary sinus and aorta in 14 patients with stable angina and one-vessel disease who underwent PTCA. Neutrophils were separated by means of the Ficoll-Hypaque system and were stimulated to detect release of elastase and generation of superoxide anion. Plasma levels of elastase were also measured by an immunoenzymatic method. PTCA was successful in all patients. Plasma elastase levels increased significantly at the end of the procedure compared with pre-PTCA values both in the coronary sinus (from 129.2 +/- 16.6 to 286.6 +/- 39.7 micrograms/l, p less than 0.005) and in the aorta (from 117.4 +/- 13.6 to 258.1 +/- 41.3 micrograms/l, p less than 0.005). On the other hand, superoxide anion released in the supernatants after neutrophil stimulation by phorbol-myristate-acetate decreased after PTCA in the coronary sinus (before PTCA, 60.1 +/- 7.1; after PTCA, 40.7 +/- 6.8 nmol 1 x 10(7) granulocytes/ml/15 min, p less than 0.05), whereas a mild but not significant decrease was observed in the aorta (from 58.3 +/- 10.9 to 55.3 +/- 8.6 nmol 1 x 10(7) granulocytes/ml/15 min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic function in patients undergoing coronary angioplasty: influence of degree of revascularization

To assess the early effects of successful coronary angioplasty on Doppler-derived left ventricular filling patterns and the significance of the extent of revascularization on these variables, 31 patients undergoing coronary angioplasty were examined within 24 h before and after the revascularization procedure. After angioplasty, the peak early to late velocity ratio increased from 0.89 +/- 0.2 to 1.05 +/- 0.3 (p less than 0.0001) and the one-third filling fraction increased from 42 +/- 10% to 48 +/- 10% (p less than 0.0001). The percent atrial contribution to filling decreased from 45 +/- 7% to 41 +/- 8% (p less than 0.01), and the pressure half-time and the isovolumetric relaxation time shortened from 55 +/- 15 to 43 +/- 13 ms (p less than 0.001) and from 100 +/- 14 to 82 +/- 17 ms (p less than 0.0001), respectively. When comparing patients with complete (n = 23) and incomplete (n = 8) revascularization, the same changes in the Doppler variables were observed. However, the mean rate of acceleration of early filling increased significantly after angioplasty only in those patients with complete revascularization. These data indicate that the left ventricular diastolic filling pattern is modified significantly as early as 24 h after successful coronary angioplasty. Improvement in impaired relaxation appears to be the most likely explanation for these changes, although increased myocardial stiffness in patients with incomplete revascularization is an alternative hypothesis.

Comparative effects of pacing-induced and flow-limited ischemia on left ventricular function

We compared left ventricular (LV) myocardial blood flow and function accompanying severe demand ischemia (rapid atrial pacing in the presence of critical bilateral coronary stenoses) and supply ischemia (complete bilateral coronary occlusion) of the same ischemic regions in 14 pentobarbital-anesthetized dogs. Pacing-induced ischemia resulted in pronounced reductions in average regional epicardial blood flow (0.8 +/- 0.4 vs. control 1.2 +/- 0.4 [+/- SD] ml/g/min, p less than 0.05) and endocardial blood flow (0.4 +/- 0.1 vs. control 1.3 +/- 0.3 ml/g/min, p less than 0.05). More severe reductions in average regional epicardial and endocardial blood flow were seen after bilateral coronary occlusion (BCO) (0.3 +/- 0.3 and 0.1 +/- 0.1 vs. control 1.3 +/- 0.3 ml/g/min, p less than 0.05, respectively). Hemodynamics of postpacing ischemia (PPi) were consistently characterized by systolic impairment including depressed systolic contractile performance [(+)dP/dtmax 1,281 +/- 442 vs. control 2,173 +/- 775 mm Hg/sec, p less than 0.05], ventricular dilation (left ventricular [LV] end-diastolic dimension [EDD] 47.6 +/- 7.8 vs. control 44.7 +/- 8.6 mm, p less than 0.05), and an increase in LV end-diastolic pressure (EDP) (14.4 +/- 2.8 vs. control 4.2 +/- 2.8 mm Hg, p less than 0.05). Abnormalities in early and late diastolic function with PPi included increased time constant of isovolumic relaxation (78.0 +/- 40.4 vs. control 46.4 +/- 20.5 msec, p less than 0.05) and increased chamber stiffness (1.9 +/- 0.77 vs. control 0.81 +/- 0.55 mm Hg/mm, p less than 0.05), respectively. The LV diastolic pressure-dimension relation, however, shifted upward and to the right in eight of nine animals, whereas an upward shift was observed in only one animal. Thus, in this model of postpacing ischemia, we observed contractile failure and passive changes in diastolic function. Alterations in ventricular function occurred consistently earlier and to a greater extent during BCO than PPi, including higher LVEDP (25.3 +/- 8.1 vs. 14.9 +/- 6.6 mm Hg, p less than 0.05), greater ventricular dilation (delta LVEDD 4.9 +/- 2.5 vs. 3.5 +/- 2.8 mm, p less than 0.05), and reduced minor-axis dimension shortening (3.3 +/- 3.1% vs. 6.5 +/- 3.6%, p less than 0.05). To detect potential qualitative differences in ventricular function between the two types of ischemia, we evaluated hemodynamics at comparable loading conditions (30 seconds to 1 minute of BCO).(ABSTRACT TRUNCATED AT 400 WORDS)

Do changes in pulmonary capillary wedge pressure adequately reflect myocardial ischemia during anesthesia? A correlative preoperative hemodynamic, electrocardiographic, and transesophageal echocardiographic study

Pulmonary capillary wedge pressure (PCWP) is monitored during anesthesia in an attempt to detect changes in myocardial function in patients at risk of preoperative cardiac complications. Because the sensitivity with which preoperative PCWP monitoring indicates myocardial ischemia is uncertain, we monitored PCWP, 12-lead electrocardiogram, and left ventricular wall motion abnormalities as defined by transesophageal echocardiography (TEE) in 98 anesthetized patients before coronary artery bypass grafting. Measurements were made five times in each patient, before and after induction of anesthesia. Myocardial ischemia was identified by TEE in 14 patients; in 10 of these, it was associated with concomitant ST segment depression of at least 1 mm. The onset of ischemia, as defined by TEE, was accompanied by a mean increase in PCWP of 3.5 +/- 4.8 mm Hg, as compared with a mean change of 0 +/- 2.2 mm Hg between observations not associated with the onset of ischemia (p less than 0.01). An increase in PCWP of at least 3 mm Hg, tested as an indicator of ischemia, had a sensitivity of 25% and a positive predictive value of 15%; after correction for background changes associated with anesthetic induction, the sensitivity of this indicator was 33%, and its positive predictive value was 16%. These figures were not improved by selecting cutoff points higher or lower than 3 mm Hg. In this study, the onset of myocardial ischemia was associated with a small yet significant increase in mean PCWP at group level.(ABSTRACT TRUNCATED AT 250 WORDS)

Left atrial function in acute transient left ventricular ischemia produced during percutaneous transluminal coronary angioplasty of the left anterior descending coronary artery

Left atrial (LA) function was studied in 32 patients during percutaneous transluminal coronary angioplasty of the proximal left anterior descending artery with a dual micromanometer positioned transseptally in the left atrium and in the left ventricle. In 10 patients LA and left ventricular (LV) cineangiography was performed 30 minutes before percutaneous transluminal coronary angioplasty and 30 seconds after the occlusion of the left anterior descending coronary artery. Thirty seconds after left anterior descending occlusion, LV peak systolic pressure decreased from 135 +/- 12 to 106 +/- 9 mm Hg (p less than 0.05) and LV maximum dP/dt decreased from 1,634 +/- 136 to 1,137 +/- 127 mm Hg/s (p less than 0.01). Simultaneously, LA mean pressure increased from 11 +/- 2 to 29 +/- 1 mm Hg (p 177 +/- 13 to 381 +/- 21 mm Hg (p less than 0.001). There was a difference between LV end-diastolic pressure and LA mean pressure of 1.5 mm Hg at rest and 7.8 mm Hg during ischemia and LA pulse pressure increased from 16 +/- 3 to 26 +/- 3 mm Hg (p less than 0.05) together with increase of LA A and V waves peak pressure. LV stroke volume index decreased from 46 +/- 5 to 43 +/- 3 ml/m2 (difference not significant). The LA maximal volume increased from 18 +/- 2 to 29 +/- 3 ml/m2 (p less than 0.001). LA volume before LA contraction increased from 29 +/- 2 to 54 +/- 3 ml/m2 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of coronary occlusion during PTCA on end-systolic and end-diastolic pressure-volume relations in humans

The influence of acute coronary occlusion on systolic and diastolic left ventricular pressure-volume relations was studied in 10 patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Pressure-volume relations were obtained by conductance catheter and micromanometer techniques and with volume load altered by transient inferior vena caval occlusion. End-systolic and end-diastolic pressure-volume relations were obtained at baseline, during 60-90 seconds of ischemia, and at return to baseline after angioplasty balloon deflation. Coronary occlusion significantly altered systolic and diastolic chamber function. Systolic dysfunction was characterized by a reproducible rightward shift of the end-systolic pressure-volume relation (+25.4 +/- 18.4 ml) that was greater for proximal left anterior descending and circumflex coronary artery occlusions (+41 ml) than for distal or right coronary artery occlusions (+15.4 ml, p less than 0.05). Occlusion also lowered chamber systolic function indexes, such as the end-systolic pressure-volume relation slope (from 4.2 to 2.8 mm Hg/ml) and preload recruitable stroke work (from 97 to 78.6 mm Hg). All systolic (and diastolic) changes were resolved with successful angioplasty. Diastolic abnormalities during angioplasty were characterized by prolonged pressure relaxation and an upward shift of the resting diastolic pressure-volume data and by an apparent increase in chamber elastic stiffness. However, when end-diastolic data from multiple beats during inferior vena caval occlusion were compared, control and ischemic end-diastolic pressure-volume relations displayed little or no difference. Thus, elevations in resting diastolic pressure-volume relations and apparent increase in chamber elastic stiffness during coronary occlusion in humans appear dominated by altered right ventricular or pericardial loading. These data indicate that pressure-volume analysis is useful in assessing the functional significance of coronary lesions and reperfusion.

Effects of graded reductions in coronary perfusion pressure on the diastolic pressure-segment length relation and the rate of isovolumic relaxation in the resting conscious dog

To assess the relations between coronary perfusion pressure, blood flow, and the diastolic pressure-segment length relation in the conscious animal, circumflex pressure was incrementally decreased in 10 resting, chronically instrumented dogs by a hydraulic occluding cuff while monitoring left ventricular pressure and regional segment length (with piezoelectric crystals) in the circumflex and left anterior descending territories. In five dogs, regional blood flow was measured by microsphere injections at selected circumflex pressures. The diastolic portion of the pressure-segment length curve was unchanged when decrements in circumflex pressure were within the autoregulatory range, that is, unassociated with changes in blood flow or systolic function. Further decrements in circumflex pressure, which decreased blood flow and regional segment shortening (both p less than 0.05), caused a progressive downward and rightward shift of the pressure-segment length curve (p less than 0.05). The rate of relaxation, as measured by tau (the time constant of pressure decay during isovolumic relaxation, which is calculated assuming either a fixed or a variable asymptote) and peak negative dP/dt, decreased slightly during reductions in circumflex pressure within the autoregulatory range and greatly at lower pressure (all p less than 0.05). Thus, in the conscious animal, reductions in coronary perfusion pressure within the autoregulatory range do not affect the diastolic pressure-segment length curve but cause modest decreases in the rate of isovolumic relaxation. Further reductions in coronary perfusion pressure, below the limits of blood flow autoregulation, cause an increased extent of relaxation with a marked downward shift of the diastolic pressure-segment length curve as well as a large decrease in the rate of relaxation.

What factors predict recovery of contractile function in the canine model of the stunned myocardium?

Recovery of contractile function of myocardium stunned by a brief, transient period of regional ischemia is highly variable. In our experience, segment shortening (an index of regional systolic contractile function) assessed during the initial hours after a 15-minute period of coronary artery occlusion in anesthetized open-chest dogs ranged from -84 to +99% of normal preocclusion values. In this retrospective study, regression analysis was used to assess the effects of various parameters on segment shortening 2 hours after reperfusion. Parameters assessed included regional myocardial blood flow both during occlusion and after reperfusion, high-energy phosphate content of previously ischemic tissue, systemic hemodynamic parameters (heart rate, mean arterial pressure and double product), occluded bed size and segment shortening measured during coronary artery occlusion. Recovery of systolic contractile function was not influenced by the degree of ischemia during coronary artery occlusion, myocardial blood flow after reperfusion, high-energy phosphate content, hemodynamic parameters or occluded bed size (correlation coefficients, r, ranged from 0.001 to 0.37 [p = not significant]). Only the degree of dyskinesia/hypokinesia exhibited during coronary occlusion significantly and reliably predicted recovery of segment shortening measured 2 hours after reflow (r = 0.70, p less than 0.001). Thus, recovery of systolic contractile function in the anesthetized canine model of the stunned myocardium is determined primarily by the degree of dysfunction exhibited during the preceding period of ischemia.

Calcium antagonists and myocardial protection

Painful and asymptomatic ischemia has been associated with left ventricular dysfunction, an important variable related to survival in patients with coronary artery disease. The treatment of patients with coronary artery disease with agents such as calcium channel blockers has been directed at reducing ischemia by restoring the balance between myocardial oxygen supply and demand, which ultimately serves to protect against myocardial dysfunction. Once ischemia has occurred, calcium channel blockers may protect myocardial cellular integrity and function. By reducing intracellular calcium overload during ischemia, mitochondrial function is preserved and adenosine triphosphate stores are maintained. Numerous in vitro and isolated heart preparations have shown that ischemia in the presence of calcium blockade is associated with less cellular dysfunction than in the situation of ischemia in the absence of calcium channel blockade.

Alterations in left ventricular relaxation, early diastolic filling and passive viscoelastic properties during postpacing ischemia

Alterations in left ventricular relaxation, early diastolic filling, regional myocardial dynamics and passive viscoelastic properties during postpacing ischemia were studied in 9 patients with coronary artery disease. In all patients typical anginal pain developed during pacing tachycardia, and in the postpacing beat, left ventricular end-diastolic pressure increased from 14 +/- 4 to 26 +/- 5 mm Hg (mean +/- standard deviation, p less than 0.01), relaxation time constant increased from 44 +/- 9 to 59 +/- 7 ms (p less than 0.01) and ejection fraction diminished from 63.1 +/- 9.1 to 52.8 +/- 10.8% (p less than 0.01). However, peak rate of early left ventricular filling obtained from frame-by-frame analysis of left ventriculograms did not change significantly. The time difference from segmental peak lengthening to left ventricular peak filling increased significantly in the ischemic segment (32 +/- 30 vs 77 +/- 49 ms, p less than 0.05). Chamber stiffness constant of a viscoelastic model increased significantly from 0.0177 +/- 0.01 to 0.0354 +/- 0.015 (p less than 0.01) without change in chamber viscosity constant. In the ischemic segment, peak rate of lengthening decreased by 45% with ischemia, and peak rate of lengthening normalized for the end-diastolic segment length by 36%. However, peak rate of lengthening normalized for the extent of systolic shortening did not change. The control segment showed a tendency to increase in these 3 parameters, but the changes were not statistically significant. Thus, peak rate of segmental myocardial lengthening decreased with ischemia because of a decrease in segmental shortening.(ABSTRACT TRUNCATED AT 250 WORDS)