Implications of inferior ST-segment depression in anterior acute myocardial infarction: electrocardiographic and angiographic correlation

This study assesses the significance of inferior ST-segment depression during anterior acute myocardial infarction (AMI) by investigating the relationship between inferior ST-segment depression and (1) the site of the left anterior descending (LAD) coronary artery lesion and (2) ST-segment deviation in the various anterior and lateral leads. We studied 126 patients with anterior AMI who underwent coronary angiography within 21 days of hospitalization. The admission 12-lead electrocardiograms were evaluated for ST-segment amplitude in each lead at 0.08 second after the J-point. Coronary angiography was evaluated for the site and severity of luminal narrowing of the coronary arteries. The site of the culprit lesion in the LAD artery, relative to the origin of the first septal and diagonal branches, was determined. In four patients no lesion was identified in the LAD artery. Of the remaining 122 patients, 40 and 53 patients had a LAD artery lesion proximal to the first septal and first diagonal branches, respectively. Additional luminal narrowing (> or = 70% of diameter) was found in the circumflex and the right coronary arteries in 27 and 37 patients, respectively. ST-segment depression of > 1 mm in leads II, III, and aVF was noted in 24, 29, and 24 patients, respectively. The prevalence of a LAD artery preseptal and prediagonal lesion was higher in patients with inferior ST-segment depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of gender in the therapeutic management of patients with acute myocardial infarction in Israel. The Israeli Thrombolytic Survey Group

A national study was performed in early 1992 in the 25 operating coronary care units in Israel, which enabled the assessment of whether the therapeutic management of patients with acute myocardial infarction was affected by patient gender. During a 2-month period, 1,014 consecutive patients with acute myocardial infarction were hospitalized. Thrombolytic therapy was given to 47% of men (362 of 769), and 43% of women (106 of 245) (p = NS). After adjustment for age, no gender differences in the administration of thrombolytic therapy were noted (odds ratio 0.95; 95% confidence interval 0.73-1.23). Coronary angiography was more frequently performed in men (22%) than in women (16%) (p < 0.05). However, no gender differences in the use of angioplasty or coronary bypass surgery performed during the index hospitalization were found (10% in men, and 8% in women). The main reasons for ineligibility for thrombolytic therapy were: late hospital arrival, absence of qualifying ST-T changes on admission electrocardiogram, and contraindications to thrombolytic therapy. Hospital death was significantly lower in patients receiving thrombolytic therapy (37 of 456; 8%) than in those excluded from thrombolysis (70 of 540;13%) (p < 0.01). This difference was significant for men, but not for women. The 1-year postdischarge mortality was 4% in patients treated compared with 12% in those ineligible for thrombolysis (p < 0.01). This significant difference persisted among men and women.

Spontaneous hemarthrosis following thrombolytic therapy for acute myocardial infarction

We describe a 45-year-old man who developed a spontaneous hemarthrosis of his right knee following thrombolytic therapy with streptokinase and rtPA for acute myocardial infarction. Surprisingly, despite the wide use of thrombolytic therapy, only four cases of spontaneous hemarthrosis following thrombolysis have been previously reported. Prompt aspiration of the joint, after stopping anticoagulant therapy, and splinting will provide early diagnosis and may prevent further damage to the joint.

Comparison of regional myocardial blood flow in syndrome X and one-vessel coronary artery disease

Myocardial blood flow (MBF) was measured using continuous inhalation of oxygen-15-labeled carbon dioxide, and positron emission tomography before and after intravenous dipyridamole in 13 patients with syndrome X (angina pectoris, angiographically normal coronary arteries, positive exercise test and negative ergonovine test), 7 healthy subjects and 8 patients with 1-vessel coronary artery disease (CAD). In patients with syndrome X, baseline MBF was greater than in healthy subjects and patients with CAD (1.24 +/- 0.27 vs 0.87 +/- 0.07 and 1.03 +/- 0.23 ml/g/min, respectively; p < 0.05), and more heterogeneous (34 +/- 7 vs 26 +/- 5 and 25 +/- 6, respectively; p < 0.05) as assessed by the coefficient of variation among myocardial regions < or = 2.3 cm3. After dipyridamole, MBF in patients with syndrome X was similar to that in healthy subjects (2.95 +/- 0.75 vs 3.40 +/- 0.82 ml/g/min; p = NS) and greater than in patients with CAD (1.78 +/- 0.76 ml/g/min; p < 0.05). However in patients with both syndrome X and CAD, MBF was more heterogeneous than in healthy subjects (48 +/- 12 and 48 +/- 11, respectively, vs 30 +/- 7; p < 0.01). Thus, in patients with syndrome X, MBF is abnormally heterogeneous both at baseline and after dipyridamole. These findings are compatible with the presence of dynamic alterations of small coronary arteries. Because these alterations appear to be very sparse within the myocardium, they can be undetected when myocardial perfusion, function and metabolism are assessed using conventional methods that are unable to detect small myocardial regions.

"Infective" myocardial infarction

Four patients who developed acute myocardial infarction (AMI) in the setting of systemic febrile illness are described. They were all treated with anticoagulants or lytic agents (or both), demonstrating patient coronary arteries following infarction. We discuss the pathogenesis and therapeutic implications of AMI occurring in this setting.

ST segment depression in a VL: a sensitive marker for acute inferior myocardial infarction

In a substantial percentage of patients with acute myocardial infarction, especially in those with inferior wall involvement, no ST elevation is detected on the electrocardiogram. In many of them, ST depression is found in leads oriented to remote segments of the heart. The importance of those reciprocal changes for early diagnosis of acute inferior myocardial infarction in patients without ST elevation has not been stressed. In order to find the prevalence of reciprocal ST depression, we evaluated the admission electrocardiograms of 107 consecutive patients with evolving first acute inferior myocardial infarction. Ninety-three patients had ST elevation of at least 0.1 mV in at least one of the inferior leads: II, III or aVF (group A) and in 14 patients ST displacement did not reach 0.1 mV in any of these leads (group B). In both groups, reciprocal ST depression occurred more frequently in aVL than in any other lead. Only three patients had no ST depression in aVL. In eight patients (7.5%) ST depression in aVL was the sole early electrocardiographic sign of the inferior infarction. aVL is the only lead that is facing the superior part of the left ventricle and thus is the only lead that is truly opponent to the inferior wall. It seems that ST depression in aVL, by contrast to that in the precordial leads, is found in the majority of patients with evolving inferior wall myocardial infarction and is not influenced by extension of the infarction to the right ventricle or to the posterior wall.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of a dipyridamole induced 99mTc-MIBI perfusion abnormality on single photon emission tomography: a quantitative validation with labelled water and positron emission tomography

To relate technetium-99m 2-methoxy-isobutyl-isonitrile (99mTc-MIBI) uptake to regional myocardial blood flow (rMBF), 99mTc-MIBI single photon emission tomography (SPET) and H2(15)O positron emission tomography (PET) scans were obtained at rest and after dipyridamole infusion in six patients with single vessel coronary artery disease. 99mTc-MIBI and H2(15)O data sets were created for each segment perfused by the stenotic vessel and for a normal reference area, assigning regions on the SPET tomograms to comparable regions on the PET by similar transaxial image reconstructions. All patients demonstrated post-dipyridamole 99mTc-MIBI perfusion defects in the territories supplied by the stenotic arteries. Resting rMBF in these regions was slightly lower than that in the normal areas (0.82 +/- 0.05 vs 0.90 +/- 0.09 ml/g/min, P = NS). A 43% +/- 14% reduction in 99mTc-MIBI activity in the area at risk was coupled with on average a 60% +/- 9% reduction in post-dipyridamole rMBF compared with control regions (0.98 +/- 0.08 vs 2.52 +/- 0.51 ml/g/min, P < 0.001). Thus, SPET assessment of 99mTc-MIBI uptake tends to underestimate the perfusion contrast between areas with normal and areas with low coronary vasodilatory reserve when compared to PET. However, these findings may still not affect the clinical usefulness of 99mTc-MIBI and more extensive studies are required to confirm these results in the clinical environment.

The incidence of atrial arrhythmias during inferior wall myocardial infarction with and without right ventricular involvement

The atrial arrhythmia profile during inferior wall acute myocardial infarction (AMI) has not been systematically examined with respect to right ventricular (RV) involvement. To this end, 62 consecutive patients with first inferior wall AMI and no other conditions known to increase susceptibility for rhythm disturbances were studied by 24-hour Holter monitoring during the first and tenth day of infarction. Based on radionuclear ventriculography performed on day 2 of infarction, patients were allocated to two groups: group A--36 patients (58%) with right ventricular ejection fraction (RVEF) less than 40% (mean +/- SD, 31 +/- 6%) and group B--26 patients (42%) with normal (greater than 40%) RVEF (mean +/- SD, 47 +/- 5%). There were no significant differences between the two groups with respect to age, sex, or left ventricular (LV) function. In the group as a whole, ectopic activity in the different categories of atrial arrhythmias was significantly higher during the first day than on the tenth day of infarction. Comparing the two groups, 33 patients (92%) in group A had a mean hourly frequency of one or more atrial premature contractions (APCs) during the first day of infarction compared with 18 patients (69%) in group B (p less than 0.001). Atrial and supraventricular tachycardia were recorded more frequently in group A patients (16 of 36 [44%] versus 8 of 26 [31%]) as well as atrial fibrillation (AF) (7 of 36 [19%] versus 1 of 26 [4%]). Quantitative analysis showed a similar trend for a higher rate of ectopic events in group A patients. Ectopic activity was neither influenced by LVEF nor by age or sex.(ABSTRACT TRUNCATED AT 250 WORDS)

A new strategy for the assessment of viable myocardium and regional myocardial blood flow using 15O-water and dynamic positron emission tomography

BACKGROUND

We have developed a new measure of myocardial viability, the water-perfusable tissue index (PTI), which is calculated from transmission, C15O, and H2(15)O positron emission tomography (PET) data sets. It is defined as the proportion of the total anatomical tissue within a given region of interest (ROI) that is capable of rapidly exchanging water and has units g (perfusable tissue)/g (total anatomical tissue). The aim of this study was to assess the prognostic value of PTI in predicting improvement in regional wall motion after successful thrombolysis for acute myocardial infarction (AMI) and to measure the myocardial blood flow to the perfusable tissue (MBFp, ml/min/g [perfusable tissue]). Furthermore, PTI was compared with 18FDG metabolic imaging in patients with old myocardial infarction (OMI).

METHODS AND RESULTS

PET scans were performed in healthy volunteers (group 1, n = 8), patients with OMI (group 2, n = 15), and in patients who were successfully thrombolysed after an AMI (group 3, n = 11). Systolic wall thickening was measured by two-dimensional echocardiography within 2-4 days of AMI and after 4 months to assess contractile recovery. In the healthy volunteers, MBFp was 0.95 +/- 0.13 ml/min/g (perfusable tissue). PTI in these regions was 1.08 +/- 0.07 g (perfusable tissue)/g (total anatomical tissue), which was consistent with all normal myocardium being perfusable by water. In the OMI group, the ratio of the relative 18FDG activity to the relative MBFp defect (metabolism-flow ratio) was calculated for each asynergic segment. Regions in which the metabolism-flow ratio was greater than or equal to 1.20 were considered reversibly injured, whereas those in which the ratio was less than 1.20 were deemed irreversibly injured. PTI in the former group of regions (n = 9) was 0.75 +/- 0.14 g (perfusable tissue)/g (total anatomical tissue) and was significantly higher than in irreversibly injured regions (n = 6) (0.53 +/- 0.12 g [perfusable tissue]/g [total anatomical tissue], p less than 0.01). Values of MBFp were similar in these segments. Seven of 12 segments in the AMI patients showed improved systolic wall thickening on follow-up. PTI in these recovery segments was 0.88 +/- 0.10 g (perfusable tissue)/g (total anatomical tissue) (p = NS versus control). PTI in the nonrecovery regions was 0.53 +/- 0.11 g (perfusable tissue)/g (total anatomical tissue), which was similar to the segments in group 2 in which 18FDG uptake was absent. MBFp was similar in both the recovery and nonrecovery segments in the subacute phase.

CONCLUSIONS

These data indicate that PTI may be a good prognostic indicator for the recovery of contractile function after successful thrombolysis and show that myocardial viability may be assessed by PET without metabolic imaging.

Ventricular tachycardia of right bundle-branch block--left axis deviation morphology and organic heart disease

Most series of patients with ventricular tachycardia (VT) of right bundle-branch block (RBBB)-left axis deviation (LAD) morphology include young individuals with no overt evidence of structural heart disease. In the present report, the clinical and electrophysiologic findings in two patients with verapamil-responsive VT and organic heart disease are described.

Electrocardiographic Q-waves inconstancy during thrombolysis in acute anterior wall myocardial infarction

It is the purpose of this paper to describe the electrocardiographic inconstancy of Q-waves during administration of thrombolytic therapy. This was documented in four patients given streptokinase early in the course of anterior wall myocardial infarction. Understanding the pathogenesis of sequential dynamic variations of Q-waves in this setting may offer important insights into coronary physiology and management of acute coronary events. We discuss the possible explanations for such changes with respect to tissue viability, dynamic vascular changes and electrophysiological properties of the reperfused infarcted myocardium.

S-T segment depression in right-sided precordial leads during acute inferior wall infarction

Right-sided chest leads (V3-V4R) were recorded in the early stages of first inferior wall acute myocardial infarction (AMI) in 100 consecutive patients. Nine patients (9%) presenting with S-T segment depression (greater than 1 mm) in these leads were subsequently studied by echocardiography and radionuclear angiography. In this group, there were 5 patients with intact right ventricular (RV) function and 4 other patients with clinical findings compatible with RV infarction. We suggest that one should not rule out RV involvement when S-T segment depression rather than elevation is seen in the right precordial leads in the presence of inferior wall AMI. An individual assessment for RV infarction is recommended when this pattern is apparent on the ECG.

Dipyridamole vasodilator response after human orthotopic heart transplantation: quantification by oxygen-15-labeled water and positron emission tomography

To assess coronary vasodilator reserve after orthotopic heart transplantation, regional myocardial perfusion was measured with oxygen-15-labeled water and dynamic positron emission tomography in 14 cardiac allograft recipients who were not experiencing rejection and who had no angiographic evidence of epicardial coronary sclerosis 15 to 73 months (mean +/- SD 43 +/- 19) after transplantation (group I). Twelve normal men with an average age of 31 years (group II) served as a control group. Regional perfusion was measured at rest and after the intravenous administration of 0.6 mg/kg body weight of dipyridamole. Rest regional myocardial blood flow was homogeneously distributed throughout the left ventricle and was significantly higher in transplant recipients (mean 1.16 +/- 0.26 ml/g per min [range 0.8 to 1.73] than in normal subjects (mean 0.85 +/- 0.13 ml/g per min [range 0.57 to 0.99]; p = 0.001) as was rest heart rate-systolic blood pressure product (rate-pressure product 11,255 +/- 2,540 vs. 7,073 +/- 1,306; p less than 0.001). After dipyridamole, perfusion in the transplant recipients was homogeneous and slightly lower (2.73 +/- 1.03 vs. 3.40 +/- 1.09 ml/g per min; p = NS), whereas rate-pressure product was slightly higher (12,179 +/- 2,266 vs. 10,885 +/- 1,895; p = NS) than the value in normal subjects. Dipyridamole vasodilator response (dipyridamole/rest myocardial blood flow) ranged from 1.23 to 4.92 (mean 2.50 +/- 1.13) in group I and from 2.65 to 5.45 (3.97 +/- 0.89) in group II (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Prazosin's effect in high renin hypertension complicating pheochromocytoma

During three consecutive days of prazosin treatment in a patient with pheochromocytoma, urinary catecholamine metabolite levels were correlated with plasma renin activity. Suppression of renin plasma activity resulted in sustained hemodynamic and clinical improvement, while no remarkable changes were observed in urinary catecholamine metabolite levels. This suggests that prazosin may interrupt the vicious cycle of worsening hypertension provoked by further activation of the renin-angiotensin system mediated by excessive circulating catecholamines.

Head-up tilt for the evaluation of syncope of unknown origin in children

Fifteen patients aged 10 to 18 years with syncope of unknown origin, and 10 healthy control children aged 11 to 18 years, were evaluated by head-up tilt to 60 degrees for 60 minutes. Six patients (43%) reproduced symptoms of syncope during the examination. Four had a typical vasovagal reaction; two had marked hyperventilation. None of the children in the control group had syncope. The head-up tilt test offers a simple, noninvasive, high-yielding diagnostic tool for evaluation of syncope in children.

Noninvasive quantification of regional myocardial blood flow in coronary artery disease with oxygen-15-labeled carbon dioxide inhalation and positron emission tomography

BACKGROUND

Oxygen-15-labeled water is a diffusible, metabolically inert myocardial blood flow tracer with a short half-life (2 minutes) that can be used quantitatively with positron emission tomography (PET). The purpose of this study was to validate a new technique to quantify myocardial blood flow (MBF) in animals and to assess its application in patients.

METHODS AND RESULTS

The technique involves the administration of 15O-labeled carbon dioxide (C15O2) and rapid dynamic scanning. Arterial and myocardial time activity curves were fitted to a single tissue compartment tracer kinetic model to estimate MBF in each myocardial region. Validation studies consisted of 52 simultaneous measurements of MBF with PET and gamma-labeled microspheres in nine closed-chest dogs over a flow range of 0.5-6.1 ml/g/min. A good correlation between the two methods was obtained (y = 0.36 + 1.0x, r = 0.91). Human studies consisted of 11 normal volunteers and eight patients with chronic stable angina and single-vessel disease, before and after intravenous dipyridamole infusion. In the normal group, MBF was homogeneous throughout the left ventricle both at rest and after administration of dipyridamole (0.88 +/- 0.08 ml/g/min and 3.52 +/- 1.12 ml/g/min, respectively; p less than or equal to 0.001). In patients, resting MBF was similar in the distribution of the normal and stenotic arteries (1.03 +/- 0.23 and 0.93 +/- 0.21 ml/g/min, respectively). After dipyridamole infusion, MBF in normally perfused areas increased to 2.86 +/- 0.83 ml/g/min, whereas in the regions supplied by stenotic arteries it increased to only 1.32 +/- 0.27 ml/g/min (p less than or equal to 0.001).

CONCLUSIONS

PET with C15O2 inhalation provides an accurate noninvasive quantitative method for measuring regional myocardial blood flow in patients.