Stress myocardial imaging in patients with mitral valve prolapse: Evidence of a perfusion abnormality

Twenty-four patients with mitral valve prolapse underwent cardiac catheterization, exercise testing, and exercise ²⁰¹thallium scintigraphy. Of 10 patients with coronary artery disease, six had abnormal scintigrams. Two of these six had exercise-induced reversible defects, two had defects that persisted during redistribution, and two had both reversible and persistent defects. Of 14 patients with normal coronary arteries, five had negative scintigrams. Of the remaining nine patients, two had exercise-induced defects, and seven (50%) had defects involving the inferior or posterior wall that persisted during redistribution. Possible mechanisms for this latter finding are discussed. In contrast to previous reports, exercise ²⁰¹thallium scintigraphy was not entirely successful in identifying patients with coronary artery disease in our patients with mitral valve prolapse.     

Cardiac function during rest and exercise in patients with mitral valve prolapse: Role of radionuclear angiocardiography

The clinical features of mitral valve prolapse syndrome and ischemic coronary disease overlap, making differentiation of the two conditions difficult. Furthermore, many patients have both conditions. This study assessed changes in ventricular function during rest and exercise in patients with mitral valve prolapse alone and in patients with prolapse and concomitant coronary artery disease. Twelve patients with angiographically documented mitral valve prolapse and normal coronary anatomy and 11 patients with normal coronary anatomy and no mitral valve prolapse had increased ejection fraction and demonstrated no wall motion abnormality during exercise. Changes in ventricular function during exercise in 11 additional patients with mitral valve prolapse demonstrated on echocardiography were similar to those in the group with mitral valve prolapse and normal coronary anatomy seen on angiography. In contrast, 6 of 11 patients with mitral valve prolapse and coronary arterial stenosis demonstrated on angiography had a decreased ejection fraction and exhibited wall motion abnormalities during exercise. These results suggest that mitral valve prolapse alone has no detrimental effect on ventricular function during rest and exercise and that exercise-induced abnormalities in ventricular function are related to the presence and severity of coronary artery disease and not to mitral valve prolapse.     

Effects of myocardial hypoxia and ischemia on myocardial scintigraphy

The effect of regional myocardial ischemia and hypoxia on myocardial scintigraphy was studied in patients and dogs after intravenous administration of cesium-129. Seven men with angiographically proved ischemic heart disease underwent exercise testing and ¹²⁹Cs was given immediately when ischemia was manifested in the electrocardiogram. Defects were not evident in the scintigrams of any patient. Failure to visualize a defect might be related to delayed uptake of ¹²⁹Cs by the myocardium (maximal uptake in 45 minutes). The ischemic state was dissipated before the disparity in uptake between normal and ischemic myocardium could be visualized. Cesium-129 is useful for identifying acute myocardial infarcts but should not be used to visualize transient exercise-induced regional ischemia.Six dogs were given ¹²⁹Cs after induction of regional myocardial hypoxia by perfusion of the anterior descending coronary artery with venous blood. In each, scintigraphy revealed a defect that resolved after reperfusion with arterial blood. Two other dogs were given ¹²⁹Cs before perfusion with hypoxemic blood; neither dog manifested a defect. Since perfusion was maintained by a pump these results suggest that the major cause of the scintigraphically observed defect was inadequate cellular uptake of ¹²⁹Cs rather than excessive cellular loss. Since regional myocardial hypoxia produced a reversible defect, scintigraphic studies might overestimate the size of an acute myocardial infarct in man by including the ischemic zone surrounding the infarct.     

Cold pressor thallium-201 myocardial scintigraphy in the diagnosis of coronary artery disease

Thallium-201 myocardial scintigraphy was performed during cold pressor stimulation in 36 patients aged 37 to 69 years. Thirty-one patients had coronary artery disease and 5 patients did not, as confirmed by coronary cineangiography. Thallium-201 (1.5 to 2 mCi) was injected at 30 seconds of the cold pressor stimulation. The product of systolic pressure × heart rate increased from a baseline of 77.4 ± 16 (standard deviation [SD]) to 103.6 ± 17 at 30 seconds of the cold pressor test (p < 0.0005). Transient perfusion deficits developed in 24 of 31 patients with coronary artery disease (sensitivity 77%), and all 5 patients without coronary artery disease had normal scintigrams. The sensitivity in detecting coronary artery disease was 40% in patients with 1 vessel disease, 91% in patients with 2 vessel disease, and 100% in patients with 3 vessel disease. Exercise electrocardiograms (available in 29 of 36 patients) were positive for ischemia in 18 of 24 patients with coronary artery disease and in 1 of 5 patients without coronary artery disease (sensitivity 75% and specificity <80%). Exercise thallium-201 scintigrams, obtained in 16 patients, were positive in 11 patients with coronary artery disease and positive cold pressor thallium-201 scintigrams. Five patients without coronary artery disease and with normal cold pressor thallium-201 scintigrams had normal exercise thallium-201 scintigrams. Coronary cineangiography performed during cold pressor stimulation in 6 patients who had positive cold pressor and exercise thallium-201 scintigrams did not show coronary spasm. Our data indicate that cold pressor thallium-201 scintigraphy offers promise as a noninvasive test in the diagnosis of coronary artery disease and may be used in patients in whom exercise testing is not feasible.     

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.     

The nature and prevalence of the abnormal exercise electrocardiogram in mitral valve prolapse.

The maximal treadmill exercise tests in 43 subjects with mitral valve prolapse were retrospectively examined and compared to those of 24 consecutive patients with abnormal maximal treadmill tests and arteriographic evidence of obstructive coronary artery disease and 21 consecutive patients with abnormal treadmill tests with evidence of neither mitral valve prolapse nor coronary artery disease at catheterization. Twelve of 43 (28%) patients with mitral valve prolapse had greater than 0.1 mv. of flat or downsloping ST depression during or following treadmill exercise. Of these 12 patients, seven (58%) were found to have the pattern of abnormal treadmill test previously described as indicative of “vasoregulatory abnormalities”; four patients satisfied the diagnostic criteria for acoustically silent mitral valve prolapse, and only one had clinical or angiographic evidence of mitral regurgitation. The finding of the “vasoregulatory” pattern of abnormal ECG response was significantly less common in the groups with abnormal treadmill tests and coronary disease and with neither coronary disease nor mitral valve prolapse (p < .0025). We conclude that the finding of an abnormal treadmill test, particularly of the type associated with “vasoregulatory abnormalities,” should lead to the suspicion of mitral valve prolapse, even in the absence of symptoms and typical auscultatory abnormalities.     

Left ventricular function in mitral valve prolapse: Assessment with radionuclide cineangiography

Abnormalities of left ventricular contraction in patients with mitral valve prolapse have suggested a myocardial factor in this disease. To determine systolic left ventricular function in mitral valve prolapse, technetium-99m gated equilibrium radionuclide cineangiography was performed in 47 patients with this diagnosis. In 39 patients without mitral regurgitation the average ejection fraction was normal at rest (average [± standard error of the mean] 57 ± 3 percent, normal 57 ± 1 percent, difference not significant) and exceeded the lower limits of normal in all but 1 patient, whose ejection fraction was 41 percent. However, ejection fraction during maximal exercise was lower for the group of patients with mitral prolapse without mitral regurgitation than for normal subjects (average 64 ± 2 percent, normal 71 ± 2 percent, p < 0.005). In eight patients with mitral prolapse and mitral regurgitation, the average ejection fraction was normal at rest but was diminished with exercise in comparison with both normal subjects and patients with mitral valve prolapse without mitral regurgitation. Chest pain, arrhythmia and the pattern or extent of mitral valve prolapse on echocardlography were not independently associated with impaired left ventricular functional reserve. We conclude that, although many patients with mitral valve prolapse have normal left ventricular function, there is a subgroup without mitral regurgitation in whom diminished left ventricular functional reserve is suggestive of a cardiomyopathic process.     

Normal coronary flow reserve in patients with mitral valve prolapse, a positive exercise test and normal coronary arteries

We studied 12 patients (eight females and four males), ages30–46 years, with echocardiographically documented mitralvalve prolapse and clinical suspicion of coronary artery disease,based on a history of chest pain (five patients), angina-likepain (three patients), a positive exercise stress electrocardiogram(12 patients) and a focally positive thallium-201 stress perfusionscan (three patients), who were referred for cardiac catheterizationand found to have normal coronary arteries. Ten patients withoutevidence of heart disease served as controls. In all mitralvalve prolapse patients, coronary flow velocity reserve wasdetermined successively in the left anterior descending, leftcircumflex and right coronary arteries as the ratio of the maximun(after intracoronary papaverine) to the resting mean coronaryflow velocity. Coronary flow reserve values were fairly similarin the mitral valve prolapse and control patients; all 12 mitralvalve prolapse patients had normal coronary flow reserve (3.5)in all three coronary arteries with no significant differencesamong the arteries tested Mean values ± 1 standard deviationof the coronary flow reserve (mitral valve prolapse vs controlpatients) were 4.7 ± 0.5 vs 4.6 ± 0.6 for theleft anterior descending, 4.6 ± 0.4 vs 4.6 ± 0.3for the left circumflex and 4. ± 0.4 vs 4.4 ±0.5 for the right coronary artery (all P=non-significant). Thesubsets of mitral valve prolapse patients with different clinical‘ischaemic’ manifestations were similar in termsof the calculated coronary flow reserve in all three major epicardialcoronary arteries. In conclusion, this study demonstrated that an inadequate regionalcoronary flow reserve does not account for the clinical manifestationsof myocardial ischaemia and positive exercise tests in patientswith mitral valve prolapse and normal coronary arteries.     

Myocardial perfusion in mitral valve prolapse with arrhythmic syndrome]

Myocardial perfusion was studied in 12 patients with mitral valve prolapse concurrent with cardiac arrhythmias by using two-dimensional 201Tl myocardial scintigraphy at rest and during exercise test. Signs of myocardial ischemia were revealed only in one case. Five patients were found to have steady-state perfusion defects whose extent correlated with the depth of mitral valve prolapse. There was an irregular distribution of myocardial blood flow, which ceased on exercise in 10 out of 12 patients. Patients with ventricular premature contraction displayed a decreased reserve of myocardial blood flow as compared to those with supraventricular premature contraction, presumably by enhancing myocardial perfusion at rest.     

Mitral valve prolapse due to coronary artery disease

Controversy exists concerning the etiologic role of coronary artery disease in the prolapsing mitral valve leaflet syndrome. A 35 year old man with progressive coronary artery disease is described. Auscultation before and after his first myocardial infarction revealed only a fourth heart sound; subsequent left ventricular cineangiography demonstrated normal anatomy and function of the mitral valve, despite extensive wall motion abnormalities. Six months later he experienced another myocardial infarction after which the typical mid-systolic click, late systolic murmur of mitral valve prolapse developed. A second left ventricular cineanglogram at this time revealed mid-systolic mitral valve prolapse and mitral regurgitation. This patient's course indicates that myocardial damage from coronary artery disease can cause mitral valve prolapse in patients without preexisting redundant mitral valve tissue.     

Thallium-201 scintigraphy in complete left bundle branch block

Nineteen symptomatic patients with left bundle branch block (LBBB) were examined by thallium-201 (TI-201) exercise scintigraphy and selective coronary arteriography. All elicited significant anteroseptal perfusion defects in the exercise scintigrams, but in only 4 was coronary artery disease (CAD) involving the left anterior descending coronary artery present. To further elucidate the effect of LBBB on septal TI-201 uptake in the absence of CAD, TI-201 scintigrams combined with regional myocardial blood flow measurements using radioactive microspheres were carried out in 7 dogs during right atrial and right ventricular pacing (LBBB in the ECG) at similar heart rates. During right atrial pacing, TI-201 uptake was homogeneous in the entire left ventricle, as were tissue flows. During right ventricular pacing, TI-201 activity was reduced to 69% of maximal TI-201 activity within the septum, whereas it averaged 90% in the lateral wall (p less than 0.05) in 6 dogs. Correspondingly, regional myocardial blood flow was lower within the septum as compared with that in the lateral wall, averaging 89 and 120 ml/min/100 g, respectively (p less than 0.005). In 1 dog, normal TI-201 distribution and tissue flows were found in both studies. Thus, symptomatic patients with LBBB may elicit abnormal TI-201 exercise scintigrams, suggesting anteroseptal ischemia despite normal coronary arteries. The electrical induction of LBBB in dogs results, in most instances, in a comparable reduction in septal TI-201 uptake associated with diminished septal blood flow. Therefore, exercise-induced septal perfusion defects in the presence of LBBB do not necessarily indicate CAD even in symptomatic patients, but may reflect functional ischemia due to asynchronous septal contraction.     

Spectrum of exercise thallium-201 myocardial perfusion imaging in patients with chest pain and normal coronary angiograms.

Twenty-seven consecutive patients with chest pain and no significant obstructive coronary lesions on arteriography were studied with thallium-201 myocardial imaging during exercise and at rest. Fifteen of the patients had typical and 12 atypical angina pectoris. All underwent treadmill exercise electrocardiographic testing; the results were abnormal in 10 patients (37 percent), normal in 14 (52 percent) and uninterpretable in 3 (11 percent). The exercise and resting thallium-201 myocardial images were normal in 23 patients (85 percent); the results of exercise testing were normal in 12 of these patients, abnormal in 8 and uninterpretable in 3. Four patients had a perfusion defect on exercise thallium-201 myocardial imaging; the defect filled in by 4 hours in two patients but persisted in the other two. In contrast, when thallium-201 myocardial imaging was performed in 28 consecutive patients with angiographic coronary artery disease, only 5 patients (16 percent) had normal exercise and resting thallium-201 myocardial images. Therefore, thallium-201 myocardial imaging offers a more effective means of identifying patients with chest pain and no obstructive coronary artery disease than the clinical history or the exercise electrocardiographic test, or both. However, 15 percent of these patients will have abnormal exercise thallium-201 myocardial images because of factors that have not yet been identified.     

Thallium-201 myocardial perfusion imaging in aortic valve stenosis

The clinical utility of thallium-201 myocardial perfusion imaging in aortic valve stenosis was evaluated at rest and after exercise in three groups of patients: (1) 20 normal subjects, (2) 11 patients with aortic valve stenosis and coronary artery disease (70 percent or greater narrowing of luminal diameter), 11 patients with aortic valve stenosis without coronary artery disease (30 percent or less narrowing). Seven of the latter 22 patients also had postoperative imaging studies. None of the normal subjects had perfusion abnormalities either at rest or after maximal exercise. Three patients with aortic stenosis and coronary artery disease and one with aortic stenosis alone had focal perfusion defects present at rest suggesting prior myocardial infarction. Five patients with aortic stenosis and coronary artery disease manifested new focal perfusion defects and also a pattern of widespread left ventricular wall “thinning” in the postexercise thallium image suggesting diffuse subendocardial ischemia; three had wall “thinning” alone, and two no change in resting focal defects. Five patients with aortic stenosis without coronary artery disease also manifested focal perfusion defects and wall thinning; one had wall thinning alone, and one a new focal defect alone. Two patients had new resting focal defects after surgery, suggesting perioperative damage, and four patients no longer had either the focal or the diffuse pattern of exercise ischemia seen preoperatively.

Thallium-201 imaging is of value in assessing the results of surgery in aortic stenosis. However, the technique does not allow adequate separation of patients with aortic stenosis and coronary artery disease from those with aortic stenosis alone because (1) angiographically significant coronary artery disease may not always produce focal ischemia before diffuse subendocardial ischemia develops, and (2) angiographically insignificant coronary artery disease may become functionally critical in the presence of aortic stenosis and produce focal ischemia.     

Normal coronary flow reserve in patients with mitral valve prolapse, a positive exercise test and normal coronary arteries

We studied 12 patients (eight females and four males), ages30–46 years, with echocardiographically documented mitralvalve prolapse and clinical suspicion of coronary artery disease,based on a history of chest pain (five patients), angina-likepain (three patients), a positive exercise stress electrocardiogram(12 patients) and a focally positive thallium-201 stress perfusionscan (three patients), who were referred for cardiac catheterizationand found to have normal coronary arteries. Ten patients withoutevidence of heart disease served as controls. In all mitralvalve prolapse patients, coronary flow velocity reserve wasdetermined successively in the left anterior descending, leftcircumflex and right coronary arteries as the ratio of the maximun(after intracoronary papaverine) to the resting mean coronaryflow velocity. Coronary flow reserve values were fairly similarin the mitral valve prolapse and control patients; all 12 mitralvalve prolapse patients had normal coronary flow reserve (3·5)in all three coronary arteries with no significant differencesamong the arteries tested Mean values ± 1 standard deviationof the coronary flow reserve (mitral valve prolapse vs controlpatients) were 4·7 ± 0·5 vs 4·6± 0·6 for the left anterior descending, 4·6± 0·4 vs 4·6 ± 0·3 for theleft circumflex and 4· ± 0·4 vs 4·4± 0·5 for the right coronary artery (all P=non-significant).The subsets of mitral valve prolapse patients with differentclinical ‘ischaemic’ manifestations were similarin terms of the calculated coronary flow reserve in all threemajor epicardial coronary arteries. In conclusion, this study demonstrated that an inadequate regionalcoronary flow reserve does not account for the clinical manifestationsof myocardial ischaemia and positive exercise tests in patientswith mitral valve prolapse and normal coronary arteries.     

Single-photon emission computed tomographic myocardial perfusion imaging in patients with mitral valve prolapse

The possibility of exercise-induced myocardial ischemia due to mitral valve prolapse (MVP) in the absence of coronary artery disease was evaluated with single-photon emission computed tomographic analysis using thallium-201 and technetium-99m sestamibi in 72 patients with MVP. Exercise electrocardiography was positive in 5 patients (8%), but single-photon emission computed tomography was found to be normal in all patients, and exercise-induced chest pain, electrocardiographic changes, and arrhythmias were found not to be related to myocardial ischemia in patients with MVP.     

Exercise-induced ST-segment changes in lead V1 identify the significantly narrowed coronary artery in patients with single-vessel disease: correlation with thallium-201 scintigraphy and coronary arteriography data

We investigated the correlation of exercise-induced ST-segment changes in lead V1, with the detection of the significantly narrowed vessel that induced ischemia during exercise in myocardial areas supplied by this vessel. We studied 198 patients who underwent exercise testing, thallium-201 scintigraphy, and coronary arteriography. The patients were divided into three groups. In group 1 (ST-segment elevation in lead V1), 84% had left anterior descending coronary artery disease (P<.001); in group 2 (ST-segment depression in lead V1), 76% had right coronary artery disease (P<.001); and in group 3 (no ST-segment changes in lead V1), there were no significant differences concerning the narrowed vessel. Thallium-201 scintigraphy data confirmed the existence of the reversible perfusion defect(s) in an area(s) of myocardium supplied by the respective coronary arteries (P<.001). Exercise-induced ST-segment elevation or depression in V1 may identify the obstructed vessel in patients with single-vessel disease and without prior myocardial infarction.     

Comparison between dobutamine echocardiography and thallium-201 scintigraphy in detecting residual stenosis,ischemia, and necrosis in patients with prior myocardial infarction

Background: Following the first attempts to detect myocardial ischemia with two-dimensional echocardiography stress testing, pharmacologic stress using dobutamine infusion has become an alternative to echocardiography exercise testing for evaluation of coronary artery disease. It has been shown that stress echocardiography has a diagnostic accuracy similar to that of an exercise thallium test. Other studies, however, indicated that radionuclide myocardial perfusion imaging was more sensitive than exercise or pharmacologic stress echocardiography for detection of ischemia or jeopardized myocardium. Hypothesis: The aim of the present study was to determine the ability of dobutamine stress echocardiography in comparison with thallium-201 scintigraphy to identify multivessel disease and the presence of myocardial scar and ischemia in 60 consecutive patients who suffered a first myocardial infarction (MI). Methods: Patients were evaluated by coronary angiography and ventriculography, thallium-201 (²⁰¹Tl) tomographic scintigraphy, and dobutamine echocardiography within 3 months of a first MI. Forty-seven had Q-wave MI and 13 had non-Q-wave MI. Eleven patients were excluded from final analysis—7 because of failure to achieve target heart rate in spite of the use of atropine, and 4 because of high blood pressure following the infusion of dobutamine. Results: Dobutamine echocardiography showed an overall sensitivity of 43% for detection of coronary artery lesions of 50–74% diameter stenosis and ²⁰¹Tl scintigraphy showed a sensitivity of 71%. For detection of lesions of ≥75% diameter stenosis, dobutamine echocardiography showed a sensitivity of 52% and ²⁰¹Tl a sensitivity of 70%. Overall agreement between wall motion and myocardial perfusion for detection of necrosis and/or ischemia in the infarct area was 40.4% with a kappa coefficient of 0.09 (p = 0.13). For detection of ischemic myocardium outside the infarct zone, overall agreement was 78.6% with a kappa coefficient of 0.49 (p<0.0001). Conclusion: Dobutamine echocardiography results showed a lower sensitivity than myocardial perfusion images in predicting multivessel coronary artery disease, and there was poor agreement between both methods in identifying necrosis or ischemia.     

Pseudoischemic “false positive” S-T segment changes induced by hyperventilation in patients with mitral valve prolapse

Hyperventilation-induced S-T segment changes that simulate myocardial ischemia have previously been noted, but the origin of this electrocardiographic finding has never been defined. To investigate further the basis for this response, the records were reviewed of 1,678 consecutive patients who underwent forced hyperventilation for 90 seconds and treadmill exercise testing. Twenty-eight patients (1.7 percent) were identified in whom hyperventilation resulted in ischemic-appearing S-T segment changes, and follow-up was possible in 21 (17 women, 4 men). Of the 21 patients, 16 (76 percent), including 15 (88 percent) of the 17 women, had evidence of mitral valve prolapse, 6 on auscultation alone, 2 on echocardiography alone and 6 with a combination of studies. Ten of the 21 patients had a negative exercise test; of the 11 patients who had a positive exercise test, only 1 had angiographic evidence of coronary arterial narrowing. The finding of ischemic-appearing S-T segment changes in response to forced hyperventilation has a high predictive value for the presence of mitral valve prolapse, particularly in women. The possible association of autonomic factors and mitral valve prolapse in the patho-genesis of an abnormal response to hyperventilation is discussed.     

Myocardial perfusion and left ventricular function during exercise evaluated by 201Tl myocardial scintigraphy and 99mTc radionuclide ventriculography in patients treated with PTCA]

To evaluate the effects of percutaneous transluminal coronary angioplasty (PTCA), we investigated myocardial ischemia and left ventricular function during exercise before and after successful PTCA in 30 patients. We used extent and severity scores of 201thallium (201Tl) exercise myocardial scintigraphy to assess myocardial ischemia and determined global and regional left ventricular ejection fraction (EF and REF) of 99mTc-RBC exercise radionuclide ventriculography to assess left ventricular function. The extent and severity scores of stress images were significantly less after PTCA than before PTCA. The scores of the redistribution images were unchanged before and after PTCA. Global EF during exercise was significantly higher after PTCA than before PTCA. There was no difference in resting global EF between before and after PTCA. Myocardial ischemia induced by exercise was semi-quantitatively analyzed as transient perfusion defect with severity score. Severity score was significantly less after PTCA than before PTCA. delta EF, which was obtained by subtraction of resting global EF from exercise one, was significantly higher after PTCA than before PTCA. However, the degree of improvement in myocardial ischemia and left ventricular function varied from patient to patient. In 17 patients with one-vessel left anterior descending artery disease, delta REF, which was determined by subtracting resting regional EF from exercise one, was significantly higher in septal and apical segments after PTCA than before PTCA. Myocardial ischemia and left ventricular function under exercise were alleviated by PTCA. However, the degree of improvement varied from patient to patient and it might have been affected by various factors including coronary dissection, edema, thrombus, restenosis, spasm, side branch stenosis or occlusion, distal thrombus, and myocardial hibernation.     

Ischemia-associated intraventricular conduction disturbances during exercise testing as a predictor of proximal left anterior descending coronary artery disease

To determine the incidence and significance of transient intraventricular conduction abnormalities occurring in association with myocardial ischemia during exercise testing, the recordings of 2,200 consecutive exercise tests were reviewed. Ten patients (0.45%) were identified as having both ischemia and intraventricular conduction abnormalities that developed transiently during the exercise test. In all 10 patients both typical angina and electrocardiographic evidence of ischemia developed during exercise. Among the 10 patients, left anterior hemiblock developed in 4, left posterior hemiblock in 2, right bundle branch block (RBBB) in 2, RBBB with left axis deviation in 1, and left anterior hemiblock progressing to complete left bundle branch block (LBBB) in 1. All 10 patients had cardiac catheterization showing significant obstruction of the left anterior descending (LAD) coronary artery at or before the origin of the first septal branch. Eight patients were treated surgically and 2 medically, all with relief of ischemic symptoms. Nine of the 10 had repeat exercise stress testing without angina or electrocardiographic evidence of ischemia and without recurrence of the transient intraventricular conduction disturbance.It is concluded that the development of transient intraventricular conduction abnormalities associated with myocardial ischemia during exercise testing is an uncommon occurrence (0.45%). When such conduction disturbances do develop, the existence of significant disease in the proximal portion of the LAD coronary artery is strongly suggested. With control of myocardial ischemia, the transient conduction disturbances during exercise are ameliorated.