Myocardial metabolic studies in prolapsing mitral leaflet syndrome

Myocardial protection using single dose del Nido Cardioplegia with and without topical cooling

INTRODUCTION

Del Nido cardioplegia (DN) is gaining acceptance in adult cardiac surgery but there is paucity of experimental data regarding its efficacy. We set out to assess the safety and efficacy of single-dose DN with and without topical cooling (TC) versus multi-dose blood cardioplegia (BC).

METHODS

Thirty-two healthy adult sheep had pressure-volume (PV) catheters placed in the left (LV) and right (RV) ventricle. Animals were assigned to receive cold (4°C) antegrade solution for a 60-min arrest using: (1) multi-dose (every 20 min) BC with TC (n = 11), (2) single-dose DN with TC (DN-C, n = 10), or (3) single-dose DN without TC (DN-H, n = 11). LV and RV PV-derived indexes, epicardial echocardiographic strains, and blood samples were acquired before CPB and at 1, 2, and 3 h of reperfusion. Dobutamine bolus (2.5 μg) was given after 3 h to test for myocardial reserve.

RESULTS

Time to rhythm restoration was shortest (54 ± 29 s, 118 ± 167 s, and 172 ± 170 s for DN-H, DN-C, and BC, respectively; p = 0.024) and number of shocks lowest (1.7 ± 1.8, 3.6 ± 2.8, and 5.6 ± 4.6 for DN-H, DN-C, and BC, respectively; p = 0.020) in DN-H group. Hemodynamic, load-independent myocardial function, echocardiographic, and metabolic data revealed only slight differences between groups. Troponin I levels did not differ between groups. With dobutamine, preload-recruitable stroke work of both LV (136 ± 50%, 131 ± 31%, 142 ± 58% for BC, DN-C and DN-H, respectively; p = 0.993) and RV (161 ± 67%, 185 ± 45%, 166 ± 75% for BC, DN-C and DN-H respectively; p = 0.580) increased similarly.

CONCLUSIONS

Single-dose DN cardioplegia with or without topical cooling offered comparable biventricular myocardial protection to multi-dose BC for a 60-min arrest in sheep.

Coronary flow reserve and ischemic-like electrocardiogram in patients with symptomatic mitral valve prolapse

The purpose of the present study was to determine whether coronary microvascular function is impaired in patients with symptomatic mitral valve prolapse (MVP) and whether ischemia-like ECG, if present, is related to coronary microvascular dysfunction. Twenty chest pain patients with normal coronary angiograms and MVP proven by echocardiogram were included. Both treadmill exercise test (TET) and coronary hemodynamic study were done in each patient. Coronary flow reserve (CFR) was determined by measuring coronary sinus flow (CSF) or great cardiac venous flow (GCVF) both at baseline and after dipyridamole 0.56 mg/kg IV for 4 minutes (maximum). All patients were divided into 2 groups with either negative (TET-) or positive results of TET (TET+). Another 10 subjects with atypical chest pain, normal coronary angiograms, echocardiogram and TET were used as controls. There were no differences in GCVF, either at baseline or after dipyridamole infusion, among the 3 groups. Calculated CFR using GCVF was similar among the 3 groups. However, baseline CSF was higher in the TET+ group (TET- vs TET+ vs control: 77 +/- 24 vs 96 +/- 31 vs 75 +/- 12 ml/min, p < 0.05) and maximum CSF was lower in the TET- group (TET- vs TET+ vs control: 167 +/- 25 vs 219 +/- 85 vs 238 +/- 80 ml/min, p < 0.05). Calculated CFR using CSF was significantly reduced in both the TET- (2.26 +/- 0.4) and TET+ groups (2.31 +/- 0.7) as compared with the control subjects (3.18 +/- 0.95, p < 0.01). There were no differences in any of the hemodynamic parameters between the TET- and TET+ groups. Coronary microvascular function could be impaired in patients with symptomatic MVP. Such impairment, when presented, was probably regional and outside the territory of the left anterior descending coronary artery. However, it was irrelevant to the presence of ischemic-like ECG during exercise.

Mitral valve prolapse, panic disorder, and chest pain

Mitral valve prolapse is a common cardiac disorder that can readily be diagnosed by characteristic auscultatory and echocardiographic criteria. Although many diseases have been associated with mitral valve prolapse, most affected individuals have the primary form of the disorder. Mitral valve prolapse is an inherited condition commonly associated with myxomatous degeneration of the mitral valve and its support structures. Complications of mitral valve prolapse, including cardiac arrhythmias, sudden death, infective endocarditis, severe mitral regurgitation (with or without chordae tendineae rupture), and cerebral ischemic events, occur infrequently considering the wide prevalence of the disorder. Panic disorder is a specific type of anxiety disorder characterized by at least three panic attacks within a 3-week period or one panic attack followed by fear of subsequent panic attacks for at least 1 month. It too is a common condition with a prevalence and age and gender distribution similar to that of mitral valve prolapse. Panic disorder and mitral valve prolapse share many nonspecific symptoms, including chest pain or discomfort, palpitations, dyspnea, effort intolerance, and pre-syncope. Chest pain is the symptom in both conditions that most commonly brings the patient to medical attention. The clinical description of chest pain in patients with mitral valve prolapse is highly variable, possibly reflecting multiple etiologies. Chest pain in panic disorder is usually characterized as atypical angina pectoris and as such bears resemblance to the chest pain commonly described by patients with mitral valve prolapse. Multiple investigative attempts to elucidate the mechanism of chest pain in both conditions have failed to identify a unifying cause. Review of the literature leaves little doubt that mitral valve prolapse and panic disorder frequently co-occur. Given the similarities in their symptomatology, a high rate of co-occurrence is, in fact, entirely predictable. There is, however, no convincing evidence of a cause-effect relationship between the two disorders, nor has a single pathophysiologic or biochemical mechanism been identified that unites these two common conditions. Until specific biologic markers for these disorders are identified, it may be impossible to do so. The lack of a proven cause-and-effect relationship between mitral valve prolapse and panic disorder and the absence of a unifying mechanism do not diminish the clinical significance of the high rate of co-occurrence between the two conditions. Primary care physicians and cardiologists frequently encounter patients with mitral valve prolapse and nonspecific symptoms with no discernible objective cause who fail to respond to beta-blockade. Panic disorder should be considered as a possible explanation for symptoms in such patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Mitral valve prolapse

Mitral valve prolapse is a common mitral valve disorder manifested clinically as a midsystolic click and/or a late systolic murmur (the click-murmur syndrome) and pathologically as billowing or prolapsing mitral leaflets (the floppy valve syndrome). Not only is it one of the two most common congenital heart diseases and the most common valve disorder diagnosed in the United States, but it is also prevalent throughout the world. Mitral valve prolapse may be associated with a variety of other conditions or diseases. Diagnosis of mitral valve prolapse should be made on clinical grounds and, if necessary, supported by echocardiography. The majority of patients with mitral valve prolapse suffer no serious sequelae. However, major complications such as disabling angina-like chest pains, progressive mitral regurgitation, infective endocarditis, thromboembolism, serious arrhythmias, and sudden death may occur. Unless these serious complications occur, most of the patients with mitral valve prolapse need no treatment other than reassurance, including those with atypical chest pain or palpitation unconfirmed by objective data. Therapy with a beta-blocker for disabling chest pain and/or arrhythmias and antiplatelet therapy for cerebral embolic events may be indicated. In occasional patients with significant mitral regurgitation surgery may be necessary.

Mitral valve prolapse. Recognizing and treating its manifestations and complications

Mitral valve prolapse is a common, multisystem syndrome for which the myxomatous mitral valve provides an anatomic hallmark. Symptoms are often unrelated to the valvular abnormality and rarely hazardous and should generally be handled conservatively. In contrast, cardiovascular complications are not rare and should be anticipated and treated aggressively.

Mitral valve prolapse: a cardiomyopathic state?

Patients with diseases of the myocardium, structural abnormalities of the heart, and valvular disease may have mitral valve prolapse demonstrated as a consequence of these disease entities. However, there appears to be a primary disease of the mitral leaflets in which left ventricular cineangiography has demonstrated abnormal contraction patterns of the left ventricle in some patients. The cause of these abnormal contraction patterns is controversial, but most of the evidence points to these abnormalities being a consequence of the abnormal leaflet tissue motion during systole creating abnormal stress on the papillary muscles and supporting left ventricle wall. Biopsy evidence of myocardial changes and abnormal cardiac metabolic studies in some patients have suggested that myocardial function may not be entirely normal in every patient with mitral valve prolapse. However, there is not sufficient evidence currently to ascribe these histologic, metabolic and angiographic changes to a primary cardiomyopathic condition.

Increased left ventricular mass in idiopathic mitral valve prolapse

We performed M-mode echocardiography on 100 subjects with idiopathic mitral valve prolapse (IMVP) and on 100 normal control subjects to determine if differences exist between the two groups in cardiac chamber size, left ventricular performance or left ventricular mass. Subjects with IMVP demonstrated significantly greater left ventricular mass than normal control subjects. There were no significant differences in fractional shortening of the left ventricle or left ventricular end-diastolic volume. There was no significant difference in left ventricular mass between asymptomatic subjects with IMVP and those with chest pain, palpitations, syncope or presyncope. Subjects with and without mitral regurgitation showed no significant difference in mass. The results indicate that subjects with IMVP demonstrate subtle left ventricular hypertrophy which does not appear to be caused by underlying organic heart disease, mitral regurgitation or sustained hypercontractility. This suggests that myocardial involvement is an integral part of the IMVP syndrome.

Assessment of diagnostic value of dipyridamole testing in angina pectoris

In order to assess the diagnostic value of dipyridamole (D) testing, we studied the responses of 34 patients with chest pain and 10 normal subjects. Blood pressure and 12-lead ECG were recorded during and after intravenous infusion of 0.6 mg/kg dipyridamole for 10 minutes. Coronary arteriography and maximal or symptom-limited exercise tests were performed in the 34 patients with chest pain. During infusion 13 patients presented ischemic ST changes and 5 with anginal pain only. The latter group had normal coronary arteries. Among the 13 patients with ischemic ST changes, 7 had at least two critical coronary stenoses and the remaining 6 had no coronary lesions. Dipyridamole tests showed poor sensitivity (44%) and specificity (39%) with respect to coronary arteriography. The relatively high number of positive responses in subjects with normal coronary arteries indicates that the coronary steal phenomenon is not the sole cause of "ischemic" response to the drug. Indirect indexes of myocardial oxygen consumption were higher in patients with a positive response to drug infusion than in those with a negative response; however the value of rate-pressure product at infusion end never reached that observed at ischemic threshold during exercise testing in the same patient. This suggests that neither can oxygen consumption increase be considered as entirely responsible for ischemic response to dipyridamole. In conclusion dipyridamole test cannot be proposed for predicting critical coronary stenoses.

Coronary artery spasm: a mechanism of chest pain in selected patients with the mitral valve prolapse syndrome

A group of 14 patients with mitral valve prolapse syndrome was referred for coronary angiographic study. The group was selected on the basis that all members had recurrent chest pain as their chief complaint and all had interpreted their chest pain as serious enough to warrant at lest two previous emergency visits to medical facilities in the six months preceding the study. All were found to have normal left ventricular function, and only one had a significant fixed obstructive coronary lesion. Seven of 14 patients (50 percent) showed evidence of coronary artery spasm during the catheterization study, five of whom had histories highly suggestive of coronary vasospasm. During the catheterization, spasm occurred spontaneously in three patients, ws ergonovine-induced in two, and was catheter-tip-induced in two. Ergonovine was administered to nine of the 14 patients. The drug induced vasospasm in two patients but failed in seven (two of whom had previously demonstrated catheter tip spasm). Of those seven patients who showed evidence of spasm, four had typical chest pain in association with reversible ST segment elevation and manifested a variant anginal syndrome.

On the role of tortuous coronary arteries in billowing mitral leaflet syndrome. A hypothesis

Sixty three male patients with billowing mitral leaflet syndrome (BML) and forty one age and sex match controls were studied with emphasis on the cineangiographic features of coronary arteries. In the BML group, the coronary arteries were considered normal in five and abnormal in fifty eight. In fifty eight with abnormal coronary arteries, twelve showed atherosclerotic occlusive lesions, fifteen showed combined occlusive lesions and nonocclusive abnormalities and thirty one showed nonocclusive abnormalities alone. The non-atherosclerotic abnormalities consisted of redundancy of the coronary arteries manifested by bizarre changes in configuration and motion. These abnormalities were present in only five patients in the Control Group. On the basis of our observations and corroborative evdience in the literature, a hypothesis is presented; the salient features of which are that: (1) the spectrum of BML may be considerably more complex than hitherto suspected, (2) a combination of BML and tortuous coronary arteries may form a distinct subset of this spectrum and (3) the increased tortuousity may result in impaired coronary perfusion causing myocardial ischemia thus offering a possible explanation for some of the symptoms - such as chest pain, arrhythmias and even sudden death seen in this syndrome.

Stress myocardial imaging in mitral leaflet prolapse syndrome

Mitral leaflet prolapse syndrome has been associated with anginal chest pain, atypical chest pain, electrocardiographic abnormalities and positive stress electrocardiograms. These features overlap those of ischemic heart disease. Furthermore, coronary artery disease is frequently associated with mitral leaflet prolapse. This study evaluated the usefulness of stress myocardial scintigraphy in distinguishing these two disorders. Thirty-two patients with an angiographic diagnosis of mitral leaflet prolapse were studied. Of the 22 patients (8 men and 14 women, mean age 48 years) with a normal coronary arteriogram, 5 had "typical" angina pectoris, 6 had resting electrocardiographic abnormalities and 6 had a positive stress electrocardiogram; all 22 patients had a normal stress myocardial scintigram. Of the 10 patients (7 men and 3 women, mean age 55 years) with at least 70 percent stenosis of one coronary artery, 6 had "typical" angina pectoris, 1 had resting electrocardiographic abnormalities and 7 had a positive stress electrocardiogram. Nine of these 10 patients had one or more demonstrable perfusion defects on stress myocardial scintigrams. It is concluded that mitral leaflet prolapse syndrome is not associated with regional myocardial ischemia as demonstrated with stress scintigraphy, and that stress scintigraphy, a noninvasive technique, is useful in distinguishing the mitral prolapse syndrome from mitral prolapse associated with coronary artery disease.

Cardiac biopsy evidence for a cardiomyopathy associated with symptomatic mitral valve prolapse

Right ventricular endomyocardial biopsy was performed in 14 patients with mitral valve prolapse to determine the existence of an associated cardiomyopathic process. All 14 patients had echocardiographic, angiographic or auscultatory evidence of mitral valve prolapse, and all were symptomatic. The group had a high incidence rate of conduction system abnormalities (50 percent) and arrhythmias (64 percent), but only one patient had a significant hemodynamic abnormality. Light microscopy revealed an increase in endocardial and interstitial fibrosis in eight patients (57 percent). Electron microscopy, performed in 11 patients, showed mitochondrial degenerative changes in all 11. Nuclear chromatin clumping, intracell edema and myocyte degeneration were frequently present. It is concluded that endomyocardial and myocardial abnormalities exist in some symptomatic patients with idiopathic mitral valve prolapse.

Left ventricular end-diastolic pressure response to atrial pacing in idiopathic mitral valve prolapse

The response of several parameters of left ventricular function to right atrial pacing was compared in 21 patients with idiopathic mitral valve prolapse and 10 normal patients. An inability to appropriately lower left ventricular end-diastolic pressure with increasing rates was demonstrated in the mitral valve prolapse group. This abnormality was not related to mitral regurgitation or factors other than ventricular performance per se.

Coronary artery spasm and mitral valve prolapse

Ten patients, representing 1.34 per cent of those patients undergoing selective coronary arteriography, were found to have unequivocal evidence of coronary artery spasm. This involved the proximal right coronary artery in eight patients, the mid-left anterior descending branch in one, and the left main coronary artery in one. Eight of these 10 patients had otherwise normal coronary arteries. Of these 10 patients with coronary artery spasm, nine had evidence of mitral valve prolapse. This involved the posteromedial scallop in six patients; the anterolateral and posteromedial scallops in one; the middle and posteromedial scallops in one; and the anterolateral, middle, and posteromedial scallops in one. These data suggest an association between coronary artery spasm and mitral valve prolapse. Coronary artery spasm may thus be an important factor in the pathogenesis of the chest pain, arrhythmias, electrocardiographic abnormalities, and sudden death, that have already been described in some patients with mitral valve prolapse.

Assessment of diagnostic value of technetium-99m pyrophosphate myocardial scintigraphy in 80 patients with possible acute myocardial infarction

The diagnostic value of technetium-99m-pyrophosphate (Tc-pyrophosphate) myocardial scintigraphy was determined in 80 consecutive patients who had been admitted to the coronary care unit in order to rule out an acute myocardial infarction. Scintigraphic findings obtained within 5 days of admission were correlated with the final cardiac diagnosis determined for each patient. Significant myocardial uptake of Tc-pyrophosphate (positive scans) occurred in 13 of 22 patients (59%) who had enzyme and/or electrocardiographic proven acute myocardial infarct: 3 out of 5 with transmural myocardial infarct, 9 of 16 with nontransmural myocardial infarct, and 1 patient with left bundle-branch block. Of 58 patients who showed no evidence of acute myocardial infarction, positive scans occurred in 14 of 33 patients who had unstable angina pectoris (42%), 0 of 6 who had congestive heart failure, 6 of 9 who had other acute cardiac syndromes, and in 0 of 10 who had noncardiac chest pain. In the patients with unstable angina pectoris positive scans could not be predicted on the basis of the history, electrocardiographic findings or the arteriographically determined severity of the coronary artery disease. Blood levels of Tc-99m activity measured in 21 cardiac patients and in 6 volunteers did not correlate with the uptake intensity of Tc-pyrophosphate. These findings suggest caution in the use of this imaging method for the diagnosis of acute myocardial infarct in patients admitted with 'rule out myocardial infarction'.

Chest pain and bilateral atrioventricular valve prolapse with normal coronary arteries in isolated corrected transposition of the great vessels. Clinical, angiographic and metabolic features

A man evaluated for disabling chest pain was found to have isolated anatomically corrected transposition of the great vessels. Angiography demonstrated right and left atrioventricular (A-V) valve prolapse and normal coronary arteries. Atrial pacing produced chest pain, ischemic electrocardiographic changes, abnormal myocardial lactate metabolism and marked elevation of the left ventricular end-diastolic pressure; all of these changes returned to normal on termination of pacing. The association of corrected transposition and bilateral A-V valve prolapse and the possible causes of myocardial ischemia in this patient are discussed.

The relationship between prolapsing mitral leaflet syndrome and angina and normal coronary arteriograms

Patients with a prolapsing mitral leaflet frequently have chest pain while their coronary arteriograms are normal. In this regard, these patients are similar to the group of patients with angina and normal coronary arteriograms. In the present study, clinical, electrocardiographic, cardiac hemodynamic, angiographic, and metabolic findings in 20 patients with a prolapsing mitral leaflet were compared to those of 16 patients with angina and normal coronary arteriograms. Except for the presence of mitral leaflet prolapse and systolic clicks, the findings were similar in both groups. We postulate that prolapsing mitral leaflet is probably related to two different mechanisms. In one the primary pathologic change is in the mitral valve (mainly myxomatous transformation), and the abnormalities of ventricular contraction are secondary to unloading of the heart because of a volume shift into the distended and enlarged mitral leaflets. In the other group, the primary pathologic change is in the myocardium, with secondary prolapse of the mitral valve. The myocardial abnormality itself is probably related to primary underlying myocardial disease or to arteriolar pathologic changes. The latter group has probably the same pathophysiologic abnormality as patients with angina and normal coronary arteriograms.