Biomechanical Testing of a Novel Device for Sutureless Nerve Repair

Suboptimal nerve end alignment achieved with conventional nerve repair techniques may contribute to poor clinical outcomes. In this study, we introduce Nerve Tape®, a novel nerve repair device that integrates flexible columns of Nitinol microhooks within a biologic backing to entubulate, align, and secure approximated nerve ends. This study compares the repair strength of Nerve Tape with that of conventional microsuture repairs. Thirty small (2 mm) and 30 large (7 mm) diameter human cadaveric nerves were transected and repaired utilizing Nerve Tape or appropriate microsuture technique. Biomechanical testing was performed using a horizontal tensile tester. The repaired nerves were loaded until failure at a distraction rate of 40 mm/min, and the maximum failure load was determined. In the small nerve groups, the load-to-failure for Nerve Tape repairs (2.33 ± 0.66 N) was significantly higher than for suture repairs (1.22 ± 0.52 N; p < 0.05). In the large nerve groups, no significant difference in load-to-failure was found between Nerve Tape (7.45 ± 2.66 N) and suture repairs (5.82 ± 1.59 N: p = 0.12). Suture repairs tended to fail by rupture, whereas Nerve Tape failures resulted from microhook pullout. Nerve Tape is a novel nerve coaptation device that provides mechanical repair strength equal or greater to clinically relevant microsuture repairs.

Microneedle cuff electrodes for extrafascicular peripheral nerve interfacing

OBJECTIVE

The work presented here describes a new tool for peripheral nerve interfacing, called the microneedle cuff (μN-cuff) electrode.

APPROACH

μN arrays are designed and integrated into cuff electrodes for penetrating superficial tissues while remaining non-invasive to delicate axonal tracts.

MAIN RESULTS

In acute testing, the presence of 75 μm height μNs decreased the electrode-tissue interface impedance by 0.34 kΩ, resulting in a 0.9 mA reduction in functional stimulation thresholds and increased the signal-to-noise ratio by 9.1 dB compared to standard (needle-less) nerve cuff electrodes. Preliminary acute characterization suggests that μN-cuff electrodes provide the stability and ease of use of standard cuff electrodes while enhancing electrical interfacing characteristics.

SIGNIFICANCE

The ability to stimulate, block, and record peripheral nerve activity with greater specificity, resolution, and fidelity can enable more precise spatiotemporal control and measurement of neural circuits.

Regenerative scaffold electrodes for peripheral nerve interfacing

Advances in neural interfacing technology are required to enable natural, thought-driven control of a prosthetic limb. Here, we describe a regenerative electrode design in which a polymer-based thin-film electrode array is integrated within a thin-film sheet of aligned nanofibers, such that axons regenerating from a transected peripheral nerve are topographically guided across the electrode recording sites. Cultures of dorsal root ganglia were used to explore design parameters leading to cellular migration and neurite extension across the nanofiber/electrode array boundary. Regenerative scaffold electrodes (RSEs) were subsequently fabricated and implanted across rat tibial nerve gaps to evaluate device recording capabilities and influence on nerve regeneration. In 20 of these animals, regeneration was compared between a conventional nerve gap model and an amputation model. Characteristic shaping of regenerated nerve morphology around the embedded electrode array was observed in both groups, and regenerated axon profile counts were similar at the eight week end point. Implanted RSEs recorded evoked neural activity in all of these cases, and also in separate implantations lasting up to five months. These results demonstrate that nanofiber-based topographic cues within a regenerative electrode can influence nerve regeneration, to the potential benefit of a peripheral nerve interface suitable for limb amputees.

Thin-film enhanced nerve guidance channels for peripheral nerve repair

It has been demonstrated that nerve guidance channels containing stacked thin-films of aligned poly(acrylonitrile-co-methylacrylate) fibers support peripheral nerve regeneration across critical sized nerve gaps, without the aid of exogenous cells or proteins. Here, we explore the ability of tubular channels minimally supplemented with aligned nanofiber-based thin-films to promote endogenous nerve repair. We describe a technique for fabricating guidance channels in which individual thin-films are fixed into place within the lumen of a polysulfone tube. Because each thin-film is <10 microm thick, this technique allows fine control over the positioning of aligned scaffolding substrate. We evaluated nerve regeneration through a 1-film guidance channel--containing a single continuous thin-film of aligned fibers--in comparison to a 3-film channel that provided two additional thin-film tracks. Thirty rats were implanted with one of the two channel types, and regeneration across a 14 mm tibial nerve gap was evaluated after 6 weeks and 13 weeks, using a range of morphological and functional measures. Both the 1-film and the 3-film channels supported regeneration across the nerve gap resulting in functional muscular reinnervation. Each channel type characteristically influenced the morphology of the regeneration cable. Interestingly, the 1-film channels supported enhanced regeneration compared to the 3-film channels in terms of regenerated axon profile counts and measures of nerve conduction velocity. These results suggest that minimal levels of appropriately positioned topographical cues significantly enhance guidance channel function by modulating endogenous repair mechanisms, resulting in effective bridging of critically sized peripheral nerve gaps.

Systolic and diastolic cardiac dysfunction early after the initiation of doxorubicin therapy: significance of gender and concurrent mediastinal radiation

Diastolic and systolic left ventricular (LV) function may be affected early after the initiation of doxorubicin therapy. However, the role of mediastinal radiation and other cytotoxic agents in the production of these early cardiac effects is unclear. In this study LV diastolic and systolic function were assessed before and after doxorubicin (223+/-122 mg.m-2; range, 40-618) in 33 patients. After doxorubicin, LV ejection fraction declined (0.61+/-0.08 to 0.56+/-0.08, P=0.0008), peak filling rate decreased (3.38+/-1.10 to 2.82+/-0.62 end diastolic volumes/s, P=0.006), and time to peak filling rate increased (162+/-39 to 182+/-45 ms, P=0.04). The changes in LV systolic and diastolic function were not related to doxorubicin dose and the use of other cytotoxic agents; the decrease in LV ejection fraction with doxorubicin was more notable in men and in patients who received mediastinal irradiation concurrently with doxorubicin. It is concluded that the use of doxorubicin was associated with the simultaneous early development of LV systolic and diastolic dysfunction. Male gender and concurrent mediastinal irradiation were independent influences, but doxorubicin dose and the use of other cytotoxic agents were not associated with worse cardiac dysfunction.

An anti-CD11/CD18 monoclonal antibody in patients with acute myocardial infarction having percutaneous transluminal coronary angioplasty (the FESTIVAL study)

Maximal benefits of coronary reperfusion after acute myocardial infarction (AMI) with ST-segment elevation may be attenuated by neutrophil-mediated reperfusion injury. Inflammatory mediators released from potentially viable myocytes cause activation of neutrophils, which traverse the endothelium and enter the myocardium. This process involves interaction between the neutrophil-expressed CD11/CD18 and endothelial-expressed intercellular adhesion molecule-1 (ICAM-1). Preclinical studies have shown that monoclonal antibodies (MAb) to CD18 can limit infarct size and preserve left ventricular function. We sought to determine the initial clinical safety and tolerability of Hu23F2G (LeukArrest), a humanized MAb to CD11/CD18, in patients with AMI who underwent percutaneous transluminal coronary angioplasty (PTCA). Sixty patients with AMI were randomized to low- (0.3 mg/kg) or high-dose (1.0 mg/kg) Hu23F2G or to placebo immediately before PTCA. We found no clinically significant differences in vital signs, physical examination, laboratory evaluation, or need for subsequent cardiac interventions. In Hu23F2G treatment groups, serum concentration of Hu23F2G increased rapidly to 3,234 +/- 1,298 microg/L (low-dose group) and 15,558 +/- 4409 microg/L (high-dose group) between 5 and 60 minutes, then declined over 72 hours to near-baseline values. Myocardial single-photon emission computed tomographic imaging 120 to 260 hours after PTCA showed no statistically significant differences in final left ventricular defect size. Hu23F2G was well tolerated, with no increase in adverse events, including infections. Thus, Hu23F2G appears safe and well tolerated in patients undergoing PTCA for AMI.

Effect of metoprolol on rest and exercise left ventricular systolic and diastolic function in idiopathic dilated cardiomyopathy

OBJECTIVE

To further characterize the effects of heart rate on systolic and diastolic function in patients with idiopathic dilated cardiomyopathy (IDCM), it was hypothesized that the relationship between heart rate and left ventricular systolic and diastolic function would be unaltered by beta-blockade and exercise.

METHODS

Eighteen patients with IDCM were randomized in a double-blind manner to receive either metoprolol or placebo for 3 months. Before and after 3 months of therapy, resting and exercise radionuclide left ventriculograms were obtained for assessment of left ventricular systolic and diastolic function.

RESULTS

At rest, metoprolol treatment compared with placebo was associated with decreased heart rate (61 +/- 11 vs 99 +/- 10 beats/min, P <.0001) and an increased left ventricular ejection fraction (0.32% +/- 0.10% vs 0.17% +/- 0.08%, P =.01). With exercise, metoprolol compared with placebo caused a decreased heart rate (86 +/- 18 vs 126 +/- 43 beats/min, P =.056), an increase in left ventricular ejection fraction (0.32% +/- 0.14% vs 0.19% +/- 0.07%, P =.052), a longer time to peak filling rate (164 +/- 21 vs 127 +/- 17 ms, P =.005), and a decreased peak filling rate (5.41 +/- 1.71 vs 8.40 +/- 1.85 stroke volumes/s, P =.012). Before beta-blockade, heart rate at rest was negatively correlated to left ventricular ejection fraction and positively correlated to peak filling rate; with exercise, the relationships of heart rate to left ventricular ejection fraction and peak filling rate were similar. After metoprolol treatment, the heart rate continued to have a similar positive correlation with the peak filling rate at rest and with exercise.

CONCLUSIONS

In patients with IDCM, systolic and diastolic cardiac function, at rest and with exercise, was related to heart rate. After beta-blockade, at rest and with exercise, diastolic function continued to be related to heart rate.

The effect of respiration on left ventricular diastolic filling as assessed by radionuclide ventriculography

Left ventricular function is modified by respiration and pericardial constraint. The aim of this study was to compare left ventricular systolic and diastolic function during inspiration and expiration in four patient groups: patients (1) without cardiac disease, (2) with severe pulmonary disease, (3) with cardiac amyloid and (4) with pericardial constriction (before and after pericardiectomy). Using blood-pool left ventriculography with modified gating, we obtained time-activity curves at the onset of inspiration and expiration. On inspiration and expiration, patients with pericardial constriction and patients with cardiac amyloid were significantly different from those without cardiac disease and those with severe pulmonary disease, in that left ventricular ejection fraction (LVEF) was less, peak filling rate was greater, time to peak filling rate was shorter, and rapid filling fraction was increased. When inspiration and expiration were compared, time to left ventricular peak filling rate was shorter (P = 0.05) on inspiration (118 +/- 48 ms) than on expiration (168 +/- 35 ms) in patients with pericardial constriction. No other measures differed between inspiration and expiration in pericardial constriction, and left ventricular function was unaffected by respiration in the other groups. Time to left ventricular peak filling rate was 49 +/- 69 ms less on inspiration than on expiration in pericardial constriction and this difference was significantly different (P = 0.04) from that in patients with cardiac amyloid (34 +/- 58 ms greater), patients without cardiac disease (2 +/- 69 ms greater) and patients with severe pulmonary disease (19 +/- 63 ms less). In pericardial constriction, pericardial resection caused an increase in LVEF without a change in left ventricular diastolic filling but abolished the differences present between inspiration and expiration in time to left ventricular peak filling rate. This respiratory response in time to left ventricular peak filling rate may be valuable in the diagnosis of pericardial constriction.

Resting heart rate and cardiac function in dilated cardiomyopathy

We hypothesized that, within the normal range of resting heart rate, heart rate and left ventricular ejection fraction would be inversely correlated and heart rate and left ventricular filling would be correlated in patients with dilated cardiomyopathy and not correlated in patients with normal cardiac function. At rest, heart rate, left ventricular ejection fraction, and three measures of diastolic filling (time to peak filling rate, peak filling rate, and first half filling fraction) were recorded using radionuclide ventriculography in subjects with no cardiac disease, patients with idiopathic dilated cardiomyopathy, and patients with dilated cardiomyopathy associated with ischemic heart disease. Heart rate had significant inverse correlations with left ventricular ejection fraction (r=-0.55, P=0.0007) and time to peak filling rate (r=-0.47, P=0.005) and a positive correlation with peak filling rate (r=0.73, P<0.0001) in patients with idiopathic dilated cardiomyopathy; heart rate was correlated only weakly with these measures in the absence of cardiac disease and essentially was not correlated in dilated cardiomyopathy due to ischemic heart disease. The change in resting heart rate with left ventricular ejection fraction and time to peak filling rate were significantly (P<0.05) different between patients with no cardiac disease and those with idiopathic dilated cardiomyopathy. Thus, resting heart rate correlated significantly with left ventricular ejection fraction and diastolic filling in patients with idiopathic dilated cardiomyopathy.

Cardiac asystole masquerading as temporal lobe epilepsy

Episodic behavior associated with impairment of consciousness is a protean clinical manifestation that may suggest a wide range of medical or neurologic disorders. We describe a patient whose symptoms of an epigastric "aura" followed by loss of consciousness suggested temporal lobe epilepsy. The episodic behavior was refractory to antiepileptic drug therapy. Prolonged video-electroencephalographic monitoring confirmed that the clinical events were cardiogenic related to asystole. Antiepileptic drug therapy was discontinued, and a cardiac pacemaker was inserted. The clinical patterns that distinguish syncope from seizures and the importance of prolonged video-electroencephalographic monitoring are discussed.

Prognostic value of exercise thallium-201 imaging in a community population

BACKGROUND

The prognostic value of exercise thallium-201 imaging has been well established in referral patient populations at tertiary care centers, but these results may be influenced by referral bias.

METHODS

This study was performed to evaluate the prognostic value of thallium imaging in a community-based population of 446 residents of Olmsted County, Minn. Eleven variables were prospectively selected and tested for their associations with outcome end points.

RESULTS

Four variables (age, history of myocardial infarction, number of abnormal thallium segments on the postexercise images, and increased thallium lung uptake) contained the most independent prognostic information. For the end point overall mortality rate, the multivariate chi-square values were 17.2 (p < 0.0001) for age and 20.9 (p < 0.0001) for the number of abnormal thallium segments on the postexercise images. Five-year survival rate for patients older than the median age of 59 years with an abnormal scan was 84% versus 97% for patients < or = 59 years of age with a normal scan.

CONCLUSION

Exercise thallium imaging was useful for prognostic purposes in this relatively low-risk community population, confirming the findings of referral population studies.

Prevalence of spontaneous reperfusion and associated myocardial salvage in patients with acute myocardial infarction

This study sought to determine the prevalence of spontaneous reperfusion of an infarct-related artery (IRA) and associated myocardial salvage in the absence of thrombolysis or angioplasty. Twenty-one patients with acute myocardial infarction received only heparin and aspirin. At a median of 18 hours after presentation, 12 patients (57%) had angiographic patency of the IRA. Technetium-99m sestamibi was injected acutely on presentation and again at hospital discharge. Acute and final perfusion defect sizes were measured. Their difference, myocardial salvage, was calculated along with salvage index (myocardial salvage/acute defect). Comparing patients with a patent versus occluded IRA, myocardium at risk was similar (16% +/- 12% vs 12% +/- 9% left ventricle, p = NS); however, myocardial salvage (9% +/- 9% vs -2% +/- 7% left ventricle, p = 0.01), and salvage index (0.62 +/- 0.37 vs 0.19 +/- 0.33, p = 0.01) were greater in patients with spontaneous reperfusion. Resolution of chest pain was greater in patients with a patent IRA (100% vs 55%, p = 0.003). Spontaneous reperfusion of the IRA occurs frequently in patients with acute myocardial infarction and is associated with significant myocardial salvage.

Association between anterior ST depression and increased myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction

PURPOSE

To determine electrocardiographic features associated with myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction.

PATIENTS AND METHODS

Ninety-two consecutive patients with acute inferior myocardial infarction were treated with reperfusion therapy in a tertiary care center. Several features were measured on the presenting electrocardiogram, including the presence or absence of ST depression in the chest leads and the total magnitudes of ST elevation or depression, and were then evaluated for their association with myocardial salvage. Myocardial salvage (% of left ventricle) was the difference between myocardium at risk and final infarct size. Tomographic myocardial perfusion imaging with technetium-99m sestamibi was performed acutely to measure myocardium at risk and repeated prior to hospital discharge to measure final infarct size.

RESULTS

The amount of myocardium at risk of infarction in the 92 patients was 19.1%+/-11.3% (range 1% to 68%), and the final infarct size was 10.6%+/-10.0% (range 0% to 45%). Thus, myocardial salvage in the 92 patients was 8.5%+/-8.4% (range -11% to 35%) of the left ventricle, or 0.51+/-0.38 (range 0.0 to 1.0) when expressed as a fraction of the myocardium at risk (salvage index). The presence or absence of anterior ST depression was the only one of seven electrocardiographic variables that was associated with myocardial salvage. Myocardial salvage was significantly greater in patients with anterior ST depression compared with those without it (10.6%+/-9.0% versus 5.9%+/-6.7%, P=0.025). Myocardium at risk was significantly greater in patients with anterior ST depression compared with those without the depression (22.8%+/-12.2% versus 14.6%+/-8.3%, P=0.0006), and infarct size tended to be larger (12.1%+/-10.4% versus 8.7%+/-9.4%, P=0.10). Myocardial salvage as a fraction of the myocardium at risk (salvage index) was similar between the two patient groups (0.52+/-0.37 versus 0.50+/-0.39, P=NS).

CONCLUSION

The presence of anterior ST depression during inferior myocardial infarction identifies a group of patients with the potential for greater myocardial salvage with reperfusion therapy. Such patients derive greater absolute benefit from reperfusion therapy because they have a larger amount of myocardium at risk, although their response to therapy (salvage index) is not intrinsically different.

Estimates of myocardium at risk and collateral flow in acute myocardial infarction using electrocardiographic indexes with comparison to radionuclide and angiographic measures

OBJECTIVES

This study sought to determine the accuracy of the initial 12-lead electrocardiogram (ECG) in predicting final infarct size after direct coronary angioplasty for myocardial infarction and to examine which physiologic variables known to be determinants of outcome the ST segment changes most closely reflect.

BACKGROUND

Myocardium at risk, collateral flow and time to reperfusion have been shown to be independent physiologic predictors of infarct size in animal and clinical models. However, such measurements may be difficult to perform on a routine basis in patients with myocardial infarction. The standard 12-lead ECG is inexpensive and readily available.

METHODS

Sixty-seven patients with acute myocardial infarction, ST segment elevation and duration of chest pain < 12 h had an initial injection of technetium-99m sestamibi. Tomographic imaging was performed 1 to 8 h later (after direct coronary angioplasty), and the images were quantified to measure perfusion defect size (myocardium at risk) and severity (a measure of collateral flow). Contrast agent injection and tomographic acquisition were repeated at hospital discharge to measure infarct size. The ST segment elevation score was calculated for each patient according to infarct location and using previously described formulas.

RESULTS

ST segment elevation score correlated closest with the radionuclide measure of collateral flow (r = -0.44, p < or = 0.0001), as well as an angiographic measure of collateral flow (r = -0.38, p = 0.05). Although ST segment elevation score correlated weakly with the magnitude of myocardium at risk by technetium-99m sestamibi, it was not as strong as infarct location alone in predicting myocardium at risk ([mean +/- SD] anterior 51 +/- 13% left ventricle vs. inferior 17 +/- 10% left ventricle, p < 0.0001). ST segment elevation score was weakly associated with final infarct size (r = 0.34, p = 0.005). A multivariate ECG model was constructed with infarct location as a surrogate for myocardium at risk, ST segment elevation score as a surrogate for estimated collateral flow, and elapsed time to reperfusion from onset of chest pain. All three variables were independently associated with infarct size.

CONCLUSIONS

The initial standard 12-lead ECG can provide insight into myocardium at risk and, to a greater extent, collateral flow and can consequently provide some estimate of subsequent infarct size. However, the confidence limits for such predictors are wide.

Effects of exercise and therapy on ventricular emptying and filling in mildly hypertensive patients

Left ventricular (LV) filling was studied in 18 healthy subjects and 19 mildly hypertensive patients before and after 50% and 70% of maximal supine exercise using radionuclide ventriculography. In addition, in the hypertensive patients, the effects of oral verapamil and lisinopril treatment on LV filling before and after exercise were studied. At rest, hypertensive patients compared with healthy subjects had a lower peak filling rate, ratio of peak filling to peak emptying rate, first-half filling fraction, and a longer isovolumic duration. With exercise, LV filling measures were not different between healthy subjects and hypertensive patients. In the hypertensive patients at rest, compared with before treatment, lisinopril prolonged isovolumic duration and verapamil had no effect on LV filling; at 50% maximal exercise compared with before treatment, verapamil shortened the time to peak filling rate and isovolumic duration and increased first-half filling fraction but, at 70% maximal exercise, verapamil had no effect, whereas lisinopril did not alter exercise LV filling at either exercise level. Thus, the early abnormal LV filling in mildly hypertensive patients is influenced by therapeutic interventions both at rest and with exercise.

Significance of anterior ST depression in inferior wall acute myocardial infarction

Early tomographic myocardial perfusion imaging with technetium-99m sestamibi was performed during inferior wall acute myocardial infarction to determine the relation between the amount and location of myocardium at risk and the presence or absence or anterior ST depression. The total size of the acute perfusion defect and its lateral and septal borders were measured in 29 consecutive patients who were admitted with > 30 minutes of chest pain and acute inferior ST elevation on their initial electrocardiogram. The 22 patients with anterior ST depression had significantly more left ventricular myocardium at risk than the 19 patients who did not have anterior ST depression (23 +/- 2% of the left ventricle vs 15 +/- 1%, p = 0.008). All 8 patients with > 25% of the left ventricle at risk had anterior ST depression. Patients with anterior ST depression had a significantly greater lateral extent of the acute perfusion defect (49 degrees +/- 8 degrees from the midinferior wall vs 23 degrees +/- 7 degrees, p = 0.002). There was no difference in the septal border of the perfusion defect between patients with and without anterior ST depression (-44 degrees +/- 4 degrees vs -46 degrees +/- 7 degrees, p = NS). No patient had a measurable anterior perfusion defect. Although there is considerable overlap between groups with and without anterior ST depression, anterior ST depression is a simple and readily available indicator of myocardium at risk in inferior wall acute myocardial infarction.

Residual flow to the infarct zone as a determinant of infarct size after direct angioplasty

BACKGROUND

In acute myocardial infarction, residual flow to the infarct zone either through antegrade flow in the infarct-related coronary artery or collateral flow from the non-infarct-related arteries is often present before reperfusion therapy. The purpose of this study was to assess the influence of antegrade flow in the infarct-related artery and/or collateral flow to the infarct zone before successful direct angioplasty on infarct size and myocardial salvage in patients with acute evolving myocardial infarction.

METHODS AND RESULTS

Sixty patients with acute evolving myocardial infarction underwent direct successful angioplasty without prior thrombolytic therapy. The myocardium at risk of infarction, the final infarct size, and myocardial salvage were measured by tomographic perfusion imaging with 99mTc sestamibi. Antegrade flow in the infarct-related artery before intervention was graded according to the Thrombolysis in Myocardial Infarction (TIMI) study group classification. Collateral flow to the infarct zone before angioplasty was also graded (0 through 3, 0 being no collateral flow). The presence of even minimal antegrade flow before angioplasty (TIMI grade 1) in the infarct-related artery compared with absent flow was associated with a significant reduction in final infarct size (9 +/- 17% versus 23 +/- 19% of left ventricle, P = .02) and a significant increase in myocardial salvage (23 +/- 16% versus 14 +/- 13% of left ventricle, P = .05) after angioplasty. When antegrade flow in the infarct-related artery was absent before angioplasty, the presence of collateral flow before angioplasty resulted in a significantly smaller final infarct size (P = .01) and more myocardial salvage (P = .05) after angioplasty. Both antegrade infarct-related artery flow and collateral flow to the infarct zone had significant independent ability to predict infarct size after angioplasty. When collateral grade and TIMI grade were added to provide an estimate of residual flow, a model including residual flow, myocardium at risk, and the interaction of residual flow and infarct site explained 83% of the variability in infarct size after angioplasty.

CONCLUSIONS

The presence of antegrade flow in the infarct-related artery and/or collateral flow to the infarct zone before direct angioplasty in acute evolving infarction results in a smaller infarct size after direct successful angioplasty.

The relationship of inferior ST depression, lateral ST elevation, and left precordial ST elevation to myocardium at risk in acute anterior myocardial infarction

The purpose of this study was to examine the relationship between the presence or absence of ST segment depression in inferior leads (II, III, and aVF) and ST segment elevation in lateral (I and aVL) or left precordial (V5 and V6) leads with the amount and location of myocardium at risk for infarction in patients with acute anterior myocardial infarction. Forty-three patients with anterior infarctions were injected with technetium 99m-sestamibi when they were first seen and underwent tomographic imaging to measure the amount and location of myocardium at risk. Patients with inferior ST depression (n = 10) compared with those without ST depression (n = 33) had perfusion defects that extended significantly further into the lateral wall (47 degrees vs 20 degrees, p = 0.04) and larger anterior injury vectors (6.47 vs 4.92, p = 0.008). There was no significant association with the percentage of myocardium at risk, disease of the right coronary artery, the presence of an inferior perfusion defect, or the size of the inferior injury vector. Among the patients with ST elevation in lateral leads (n = 16) compared with those without (n = 27), there was a significantly more lateral defect border (47 degrees vs 25 degrees, p = 0.007) and a larger anterior injury vector (6.07 vs 4.81, p = 0.01). There was no significant correlation with the percentage of myocardium at risk. A significant relationship could not be demonstrated between the presence of ST elevation in the left precordial leads and any measure of the amount or location of myocardium at risk. These data support the theory that inferior ST depression in patients with transmural anterior ischemia is a "reciprocal" finding and does not represent inferior ischemia. The presence of inferior ST depression or lateral ST elevation is associated with a more lateral perfusion defect. Neither of these ECG findings is associated with the amount of myocardium at risk for infarction.

Use of the internal mammary artery for myocardial revascularization in a patient with radiation-induced coronary artery disease

A 9-year-old boy with clinical stage IIA Hodgkin's disease underwent radiotherapy to the neck and mediastinum. Twenty-two years later, he sought medical attention because of angina pectoris. Cardiac catheterization revealed proximally located high-grade stenoses of the left main, left anterior descending, circumflex, and right coronary arteries. He underwent coronary artery bypass grafting with use of the left internal mammary artery to the left anterior descending coronary artery and reversed saphenous vein grafts to the circumflex and right coronary arteries. The postoperative course was uncomplicated. Previous radiotherapy to the mediastinum should be considered a risk factor for the development of premature coronary artery disease. Surgical revascularization is the preferred method of management. A combination of an internal mammary artery graft and a saphenous vein graft should be used in young patients.

Electrocardiographic prediction of myocardial area at risk

The 12-lead electrocardiogram in 23 patients with an evolving first myocardial infarction (12 anterior and 11 inferior) was correlated with the myocardial area at risk measured by tomographic perfusion imaging with technetium-99m sestamibi. Of several electrocardiographic factors, only the extent and quantity (with and without R-wave normalization) of ST depression differed significantly between inferior and anterior evolving infarction. The myocardial area at risk was greater in anterior than in inferior evolving infarction. The extent of the myocardium at risk correlated modestly (r = 0.58) with total ST displacement in anterior evolving infarction and with total ST depression normalized to the R wave (r = 0.70) in inferior evolving infarction. Because of the large standard errors (9 to 15% of the left ventricle), estimates of the myocardial area at risk based on these electrocardiographic variables have minimal clinical value in the individual patient.

Influence of left ventricular diastolic filling on symptoms and survival in patients with decreased left ventricular systolic function

The relation between left ventricular (LV) filling variables measured by gated blood pool radionuclide ventriculography and clinical symptoms and survival was examined in 93 patients who had decreased LV systolic function. The diastolic data were not significantly associated with clinical symptoms. Time to peak filling rate, peak filling rate and ejection fraction were associated independently with survival free of cardiac death (chi-square = 7.74, 5.91 and 3.92, respectively, by stepwise Cox regression analysis). A short time to peak filling rate or increased peak filling rate was associated with decreased survival, whereas the opposite indicated a good prognosis. One-year Kaplan-Meier survival was 73 and 98% when time to peak filling rate was below or above the median value of 167 ms, respectively, 82 and 90% when peak filling rate was above or below the median value of 1.67 end-diastolic volumes per second, respectively, and 76 and 95% when LV ejection fraction was below or above the median value of 0.35, respectively. Thus, filling variables (time to peak filling rate and peak filling rate) measured by radionuclide ventriculography may be valuable in predicting survival in patients with decreased LV systolic function.

Noninvasive identification of myocardium at risk in patients with acute myocardial infarction and nondiagnostic electrocardiograms with technetium-99m-Sestamibi

BACKGROUND

Patients who have chest pain without electrocardiographic ST elevation are not candidates for thrombolytic therapy in most clinical trials. This study examined the value of technetium-99m-Sestamibi tomographic imaging to assess myocardial perfusion in patients during chest pain without ST elevation.

METHODS AND RESULTS

Tc-99m-Sestamibi was injected in 14 patients who had chest pain without ST elevation, who subsequently developed enzymatic evidence of myocardial infarction within 24 hours. Tomographic imaging was performed 1-6 hours after injection. Thirteen of 14 patients showed significant perfusion defects indicative of acute myocardial infarction consistent with absent perfusion (20 +/- 15% of the left ventricle; range, 2-53%); one patient had normal images. Because of the absence of definitive electrocardiographic changes, only five patients received reperfusion therapy within 6 hours of the onset of chest pain. Regional wall motion abnormalities were present in nine of nine patients undergoing contrast ventriculography and correlated with the location of the Tc-99m-Sestamibi perfusion defect. At the time of subsequent coronary angiography, total arterial occlusion was present in 11 of the 14 patients. The infarct-related artery could be identified in 13 of the 14 patients. In six of these 13 patients, the left circumflex was the infarct-related artery.

CONCLUSIONS

Patients who have chest pain without electrocardiographic ST elevation may have arterial occlusion and significant myocardium at risk. Tc-99m-Sestamibi imaging may be of benefit in identifying these patients early so that they can be considered for acute reperfusion therapy.

Limitations of the electrocardiogram in estimating infarction size after acute reperfusion therapy for myocardial infarction

OBJECTIVE

To assess the ability of the 12-lead electrocardiogram to estimate infarction size after reperfusion therapy for acute myocardial infarction.

DESIGN

The presence or absence of Q waves and the Selvester QRS score obtained before and after hospital discharge were compared with radionuclide estimates of infarction size and ejection fraction at discharge and 6 weeks later, regional wall motion at discharge and 6 weeks later, and myocardial perfusion defect size quantitated with Tc-99m-sestamibi at discharge.

SETTING

A tertiary referral center.

PATIENTS

A consecutive series of 43 patients with acute myocardial infarction who received acute reperfusion therapy and were assessed using 12-lead electrocardiography, radionuclide angiography, and Tc-99m-sestamibi tomographic imaging before discharge.

INTERVENTIONS

All 43 patients received acute reperfusion therapy: 21 patients received intravenous tissue plasminogen activator, and 22 patients underwent primary percutaneous transluminal coronary angioplasty.

MAIN OUTCOME MEASURE

The correlation of QRS score and Q waves with three radionuclide estimates of infarction size.

RESULTS

A significant correlation was found between myocardial perfusion defect size at discharge and both left ventricular ejection fraction and regional wall motion at discharge and 6 weeks later (r = -0.71 to -0.81; all comparisons, P less than 0.001). Little correlation was found between electrocardiographic findings and radionuclide measurements of left ventricular function and perfusion. Presence or absence of Q waves at discharge was not associated with any difference in ejection fraction, regional wall motion, or perfusion defect at discharge. No correlation was found between QRS score and ejection fraction or myocardial perfusion defect size at discharge. The QRS score at discharge correlated only weakly with regional wall motion at discharge and 6 weeks later. This lack of correlation was unchanged when electrocardiograms obtained after hospital discharge were analyzed.

CONCLUSION

Although inexpensive and readily available, the 12-lead electrocardiogram does not appear to provide a reliable estimate of infarction size after reperfusion therapy for acute myocardial infarction.

Comparison of exercise performance in left main and three-vessel coronary artery disease

From a consecutive series of patients who underwent rest and exercise radionuclide angiography over several years, we retrospectively identified 34 patients with left main coronary artery disease and 103 patients with three-vessel coronary artery disease who did not have significant left main disease. The results of gated equilibrium radionuclide angiography were compared in these 2 groups. Multiple exercise hemodynamic, exercise electrocardiographic, and exercise radionuclide angiographic parameters were considered in an attempt to separate the 2 groups. The only parameter that was significantly different between the 2 groups was exercise heart rate. However, no value of the exercise heart rate could meaningfully separate the 2 groups. Despite their known difference in prognosis, patients with left main and three-vessel disease had very similar exercise performance and could not be distinguished from one another by exercise electrocardiography or exercise radionuclide angiography. The inability to distinguish these two groups is a clear limitation of noninvasive exercise modalities.

Determination of diastolic function by radionuclide ventriculography

Diastolic filling can be measured by radionuclide ventriculography with use of several techniques including those based on gated and list-mode acquisitions, the first-pass method, and the nuclear probe. Radionuclide ventriculography specifically assesses volumes, rates of volume change, and intervals during ventricular filling. Normal values for diastolic filling measurement vary depending on the individual radionuclide methods used and the age of the patient. Comparative studies of the radionuclide method with contrast angiographic and Doppler echocardiographic techniques for measuring diastole are discussed, and the advantages and disadvantages of the radionuclide techniques are explored. The role of radionuclide assessment of diastolic function in specific clinical examples of hypertrophic cardiomyopathy, hypertension, anthracycline-induced cardiomyopathy, and coronary artery disease is reviewed. Radionuclide ventriculography is an accurate and easily applicable procedure for studying left ventricular volume changes in diastole.

Prevention of late ventricular dilatation after acute myocardial infarction by successful thrombolytic reperfusion

To examine the sequential changes in left ventricular volume after thrombolytic therapy for acute myocardial infarction, gated radionuclide ventriculography was performed within 12 hours of thrombolysis and at 1 and 6 weeks in 34 consecutive patients who received intravenous thrombolytic therapy in the Thrombolysis in Myocardial Infarction Trial. Angiographic confirmation of immediate reperfusion (mean 5.6 hours after onset of symptoms) that persisted at 24 hours was noted in 24 patients; 10 patients were not reperfused. A small (9.5%), but significant (p = 0.05), increase in end-diastolic volume index was noted in the reperfused group between 1 and 6 weeks; however, a marked degree of dilatation (35%) was noted in the non-reperfused group (p = 0.01). The change in left ventricular volume between 1 and 6 weeks differed in the 2 groups for both end-diastolic volume index and end-systolic volume index (p = 0.01 and p = 0.02, respectively). By 6 weeks, both end-diastolic volume index and end-systolic volume index were greater in the nonreperfused group (p less than 0.05). Between the acute and 6-week studies, definite increases in end-diastolic volume index (p less than 0.05) and end-systolic volume index (p less than 0.01) occurred commonly in the nonreperfused group but rarely in the reperfused group. Compared to the nonreperfused group, the reperfused group also had significantly higher ejection fractions at both 1 and 6 weeks (p less than 0.05). The change in end-diastolic volume index between 1 and 6 weeks correlated significantly and inversely with the ejection fraction at 1 week (r = -0.60, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Supine exercise electrocardiography compared with exercise radionuclide angiography in noninvasive identification of severe coronary artery disease

STUDY OBJECTIVE

To determine the incremental value of exercise radionuclide angiography for identification of severe coronary artery disease.

DESIGN

Retrospective analysis comparing logistic regression models.

SETTING

A tertiary care referral center.

PATIENTS

Three hundred and ninety-one consecutive patients who had normal resting electrocardiograms (ECGs) and no digoxin therapy within the previous week.

MEASUREMENTS AND MAIN RESULTS

The exercise ECG model, consisting of magnitude of ST depression, exercise heart rate, and patient gender, was highly predictive of three vessel or left main coronary artery disease (chi 2 = 100, P less than 0.0001). The model correctly classified 60% of the study group which included 56 patients with and 179 without severe disease. The addition of radionuclide angiographic variables improved the predictive power of the model (chi 2 = 124, P less than 0.0001). However, the exercise radionuclide angiographic variables increased the number of patients who were correctly classified by only 11 and the percentage by 3% (to a total of 63% of the study group).

CONCLUSIONS

The modest additional advantage provided by exercise radionuclide angiography for identification of three vessel or left main coronary artery disease in patients with normal resting ECGs would not appear to justify its routine use for this purpose. Before this conclusion is used as a guide for clinical practice, our results should be prospectively confirmed in a separate sample of patients in another institution.

Left ventricular systolic response to exercise in patients with systemic hypertension without left ventricular hypertrophy

Supine exercise radionuclide angiography was performed in 367 men to assess left ventricular (LV) systolic response to exercise; 58 had systemic hypertension without LV hypertrophy on a resting electrocardiogram and 309 were normotensive. All patients met the following criteria defining a low pretest likelihood of coronary artery disease: age less than 50 years; normal electrocardiographic response to exercise; absence of typical or atypical chest pain; and exercise heart rate greater than 120 beats/min. Patients taking beta-receptor blockers were excluded. There were no significant differences between hypertensive and normotensive groups in peak exercise heart rate, workload or exercise duration. However, hypertensive patients had significantly higher peak exercise systolic blood pressures and peak exercise rate-pressure products. There were no differences between patients with and without hypertension in resting ejection fraction, peak exercise ejection fraction (hypertensive patients 0.71 +/- 0.01, normotensive patients 0.70 +/- 0.05) or change in ejection fraction at peak exercise (hypertensive patients 0.07 +/- 0.01, normotensive patients 0.07 +/- 0.04). Diastolic and systolic ventricular volumes tended to be smaller in the hypertensive patients, but the difference was not statistically significant. The change in systolic volume with exercise was similar in the 2 groups (hypertensive -10 +/- 3 ml/m2, normotensive -10 +/- 1 ml/m2). In the absence of electrocardiographic evidence of LV hypertrophy, systemic hypertension does not influence LV systolic response to exercise.

Influence of age and sex on left ventricular filling at rest in subjects without clinical cardiac disease

Left ventricular (LV) filling at rest was studied by radionuclide ventriculography using alternate R-wave gating in 42 patients (29 men, 13 women) who had a low likelihood of cardiac disease. LV filling measurements differed little between men and women. Age was correlated positively with atrial filling duration (r = 0.55), atrial filling duration fraction (r = 0.52) and atrial filling fraction (r = 0.56) and negatively with rapid filling fraction (r = -0.58). Age was not correlated with peak filling rate, time to peak filling rate and first-half filling fraction. The heart rate at rest was significantly negatively correlated with rapid (r = -0.62), slow (r = -0.81) and atrial (r = -0.72) filling durations, but not with isovolumic duration. The heart rate at rest was weakly positively correlated with peak filling rate in end-diastolic volume per second (r = 0.36) and negatively correlated with first-half filling fraction (r = -0.35). Systolic pressure at rest influenced atrial filling duration. LV ejection fraction and end-diastolic volume index were not correlated significantly with LV filling in relatively normal subjects.

Myocardial stunning in hypertrophic cardiomyopathy: recovery predicted by single photon emission computed tomographic thallium-201 scintigraphy

A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.

Gender-related differences in cardiac response to supine exercise assessed by radionuclide angiography

This study examines the recently reported gender differences in cardiac responses to exercise. The study group consisted of 192 men and 67 women with a low probability of coronary artery disease who underwent supine exercise radionuclide angiography. Men had a lower rest ejection fraction than that of women (0.63 versus 0.66, p = 0.02) and greater increases in ejection fraction with exercise (0.08 versus 0.02, p = 0.0001). The slope relating ejection fraction to metabolic equivalents of exercise (METs) was greater (p = 0.004) for men, even after adjustment for differences in rest ejection fraction and end-diastolic volume index. Compared with men, women had a smaller rest end-diastolic volume index (87 versus 97 ml/m2, p = 0.003) and a greater increase in end-diastolic volume index with exercise (6 versus -2 ml/m2, p = 0.002). The slope relating end-diastolic volume to METs was greater for women, even after adjustment for differences in rest end-diastolic volume index and peak work load. There are clear gender differences in the supine exercise response of ejection fraction and end-diastolic volume that are not explained by differences in exercise capacity.

Significance of T-wave pseudonormalization during exercise. A radionuclide angiographic study

In 84 consecutive patients with resting T-wave inversion, radionuclide angiography revealed significant new wall motion abnormalities in 13 (28 percent) of the 47 patients with persistent T-wave inversion and in 23 (62 percent) of the 37 patients with T-wave pseudonormalization during exercise (p less than 0.01). The response of the ejection fraction to exercise was better in patients with persistent T-wave inversion than in those with pseudonormalization (p less than 0.04). Mechanical evidence of ischemia was seen in 14 (61 percent) of the 23 patients with T-wave pseudonormalization but without ST-segment depression. In patients with resting T-wave inversion, pseudonormalization was slightly more sensitive but less specific than a positive exercise test for predicting significant new wall motion abnormalities or decreases in the ejection fraction with exercise. Although pseudonormalization is not extremely useful alone, the presence or absence of this finding can increase the diagnostic accuracy of exercise electrocardiography in patients with resting T-wave inversion and suspected ischemic heart disease.

Diastolic measurements from alternate R-wave gating of radionuclide angiograms

Left ventricular diastolic filling measurements were determined by means of standard consecutive R-wave gating, list mode acquisition, and alternate R-wave gating. Time-activity curves obtained by the latter two methods were equally accurate in quantifying rapid, slow, and atrial left ventricular filling, whereas curves obtained by means of standard gating were inadequate for this purpose.

Prognostic value and limitations of exercise radionuclide angiography in medically treated coronary artery disease

We investigated whether exercise radionuclide angiography provides prognostic information in addition to that identified by resting left ventricular function and coronary anatomy in patients with medically treated coronary artery disease. Clinical follow-up (median, 21.7 months) was obtained in 424 medically treated patients who underwent exercise radionuclide angiography and coronary angiography. The mean age of the study population was 58 years, and 67% were men. Cardiac death occurred in 16 patients, nonfatal myocardial infarction in 16, and nonfatal out-of-hospital cardiac arrest in 1. Univariate analysis showed that multiple variables were associated with future cardiac events, including number of diseased vessels, exercise and rest radionuclide ejection fraction, history of myocardial infarction, exercise and rest left ventricular end-systolic and end-diastolic volume indices, peak exercise workload, age, abnormal resting electrocardiogram, and peak exercise ST-segment depression. Only three variables were independently associated with cardiac events on follow-up: number of diseased vessels, radionuclide ejection fraction at rest, and age. In patients with three-vessel disease and a resting radionuclide ejection fraction of more than 40%, a subgroup with higher risk could not be identified on the basis of exercise radionuclide response.

Stability of radionuclide left ventricular volume measurements

Left ventricular volume measurements are useful in the evaluation of cardiac function and are important in the long-term management of patients with various cardiac diseases. Although there are many methods of measuring left ventricular volumes, a non invasive and reproducible method relies on radionuclide techniques. The errors in estimation of left ventricular volumes have previously been well studied. To date there is little information on the reproducibility of left ventricular volume measurements made by this technique at different points in time. This study evaluated 61 patients with stable coronary artery disease over a period of approximately 1 year. All patients had two resting radionuclide gated blood pool studies. Patients had no changes in symptoms, electrocardiographic findings or medication between studies. Using +/- 2 SD as 95% confidence limits for a true change, an end diastolic volume index change greater than -34 ml m-2 and +38 ml m-2 or an end systolic volume index change greater than -24 ml m-2 and +26 ml m-2 are required to state with confidence that a change has occurred between two examinations. These data provide guidelines to assess whether interval changes in left ventricular volumes are real or are due to variations within the technique.

Noninvasive identification of severe coronary artery disease using exercise radionuclide angiography

The ability of exercise radionuclide angiography to predict the risk of having significant left main or three vessel coronary artery disease was examined in 681 patients who underwent both radionuclide and coronary angiography. There were significant differences in multiple variables between patients with or without such disease. Logistic regression analysis identified seven variables as independently predictive of the presence of left main or three vessel disease. Using these variables, low, intermediate and high probability groups could be identified. The four most important variables--the magnitude of exercise ST segment depression, peak exercise ejection fraction, peak exercise rate-pressure product and sex of the patient--can provide practical estimates of the risk of having left main or three vessel disease. Exercise radionuclide angiography can provide a clinically useful noninvasive estimate of the risk of having significant left main or three vessel disease.

Guidelines for the interpretation of the exercise radionuclide ventriculogram for diagnosing coronary artery disease

In 622 patients with known coronary artery anatomy, heart rate (HR).blood pressure (BP) product and left ventricular (LV) ejection fraction (EF) at maximal supine exercise measured by radionuclide ventriculography were used to estimate, by logistic regression analysis, the probabilities of absence of significant coronary artery disease (CAD), presence of significant CAD, presence of multivessel CAD and presence of 3-vessel CAD. Thus, for example, estimated probabilities of each of the aforementioned 4 categories of CAD are 0.39, 0.61, 0.32 and 0.12, respectively, for HR.BP product of 26,000 beats.mm Hg/min and LVEF of 0.6 at maximal exercise and 0.08, 0.92, 0.77 and 0.48, respectively, for HR.BP of 15,000 and LVEF of 0.4. The graphic presentations of these estimated probabilities form useful guidelines for interpreting the results of exercise radionuclide ventriculography. In addition, specific cutoff values at maximal exercise defined 2 groups: (HR.BP product greater than or equal to 21,000 beats.mm Hg/min and LVEF greater than or equal to 0.55) with a high (70%) likelihood of absence of significant CAD or 1-vessel CAD and a low (7%) likelihood of 3-vessel CAD, and (HR.BP product less than 21,000 and LVEF less than 0.55) with a high (72%) likelihood of multivessel CAD and a low (8%) likelihood of absence of CAD.

Exercise response of the systolic pressure to end-systolic volume ratio in patients with coronary artery disease

The exercise response of the ratio of systolic blood pressure to end-systolic volume was studied in 243 patients with chest pain and coronary artery disease who underwent supine rest and exercise equilibrium radionuclide angiography. There was a wide variation in both rest and exercise variables in this group. The exercise response of the systolic pressure/volume ratio also varied greatly, ranging from a decrease of 59% to an increase of 136%. Twenty-one clinical, catheterization and radionuclide angiographic variables were examined to determine their relation to the exercise response of the systolic pressure/volume ratio; nine variables were individually correlated with this ratio. Multiple regression analysis identified the change in end-diastolic volume index with exercise, rest systolic blood pressure, coronary artery Gensini score and peak work load as significant independent predictors of the exercise response of the systolic pressure/volume ratio; the latter correlated significantly with the change in ejection fraction with exercise (r = 0.73, p less than 0.0001). Its sensitivity for the detection of coronary artery disease in the study group (84%) and its "normalcy rate" in a group of 120 patients with a low likelihood of coronary artery disease (81%) were similar to those of the peak exercise ejection fraction (75 and 82%, respectively). These results demonstrate that the exercise response of the systolic pressure/end-systolic volume ratio is a complex response that is influenced by several pathophysiologic variables in the presence of coronary artery disease. It does not offer any advantage over ejection fraction measurements for the detection of exercise-induced ischemia.

Anatomic and functional significance of a hypotensive response during supine exercise radionuclide ventriculography

The significance of a decline in systolic blood pressure (BP) during supine exercise was examined in 820 patients who underwent both supine exercise gated equilibrium radionuclide ventriculography and coronary angiography. Twenty-seven patients, 3% of the study population, had a decrease in systolic BP at peak exercise of more than 10 mm Hg from the systolic BP at rest. Other indicators of ischemia--angina, ST-segment depression, a decrease in ejection fraction and wall motion abnormality during exercise--were present frequently but not uniformly in these patients. Although most patients had a decline in ejection fraction and a new wall motion abnormality with exercise, 4 patients had an increase in ejection fraction with exercise without any regional wall motion abnormalities. Coronary angiography in the 27 patients with systolic hypotension demonstrated severe coronary artery disease (CAD). Twenty-two patients (81%) had 3-vessel or left main CAD. Twenty of these 22 patients with 3-vessel CAD had at least 2 arteries with 90% or more diameter stenoses. Systolic hypotension during supine exercise radionuclide angiography is infrequent, usually associated with evidence of global and regional left ventricular dysfunction, and a marker of very severe CAD.

Cardiac involvement in Lyme disease: manifestations and management

Cardiac involvement in Lyme disease may manifest as atrioventricular block, myopericarditis, and left ventricular dysfunction. Diagnosis depends on recognition of the systemic nature of Lyme disease, including cardiac involvement, and its natural history. Serologic tests that are both sensitive and specific may aid in diagnosis. Although current recommendations for the treatment of Lyme disease with carditis include antibiotics and salicylates or corticosteroids, these types of therapy have not been unequivocally demonstrated to alter the natural history of cardiac involvement. Supportive therapy may necessitate temporary transvenous cardiac pacing in symptomatic patients.

Exercise radionuclide ventriculography in evaluation of coronary artery disease

The ability of radionuclide variables obtained at rest and at peak exercise to discriminate the number of stenosed (greater than or equal to 70% luminal diameter narrowing) major coronary arteries was evaluated in 296 patients undergoing supine exercise radionuclide ventriculography. Stepwise linear discriminant analysis of the data from the first 200 patients identified a significant (p less than 0.001) discriminatory combination. Application of this function to the remaining 96 patients provided correct classification of arteriographically determined zero, one, two, and three stenosed arteries in 59%, 18%, 14%, and 60% of cases, respectively. The discriminant function classified minimal stenoses (zero or one artery) and multivessel stenoses (two or three arteries) correctly by arteriography in two thirds of cases in each group. Arteriographic presence of three stenoses was unlikely in those classified as having no stenosis, and absence of stenosis was rare in those classified as having three stenoses. Exercise radionuclide ventriculography is most helpful in identifying minimal and multivessel coronary disease rather than number of stenosed major coronary arteries.

Reproducibility of noninvasive tests of peripheral occlusive arterial disease

We studied the reproducibility of four tests of peripheral occlusive arterial disease in 54 subjects, 32 of whom had this disease. We found that the reproducibility of systolic blood pressures obtained at rest from the thighs, calves, and ankles approximated that of arm systolic and diastolic blood pressures, as did the ankle-to-arm systolic blood pressure ratios. The average of the tenth and ninetieth percentile ranges of the resting systolic blood pressure ankle-to-arm ratios was +/- 0.10. Systolic blood pressures from the fingers were somewhat less reproducible, and those from the toes were even more variable. Systolic blood pressure ankle-to-arm ratios measured after the patient had exercised were less reproducible than resting ratios. The average of the tenth and ninetieth percentile ranges of the 1-, 3-, 5-, and 10-minute ratios after exercise was -0.13 to +0.16. Skin temperatures from the fingers and toes were approximately as reproducible as systolic blood pressures from the arms and legs and as the resting ankle-to-arm blood pressure ratios. Pulse-volume recordings from the thighs, calves, ankles, feet, toes, and fingers were very poorly reproducible. We conclude that information on the reproducibility of these measurements is essential in the evaluation of noninvasive arterial tests that are used to determine the course of peripheral occlusive arterial disease.

Cardiovascular hemodynamics of bicycle and handgrip exercise in normal subjects before and after administration of propranolol

Radionuclide angiography was used to study the effects of supine and upright bicycle exercise and handgrip exercise in 17 (12 well-trained) normal subjects before (control) and immediately after the administration of propranolol (160 mg/day for 4 days). Cardiac hemodynamic values were related to position in that control left ventricular volumes and the cardiac index were greater in the supine position than in the upright at rest but resting left ventricular ejection fraction was similar in both positions. The pressure volume index was greater in the upright position than in the supine. At maximal exercise before treatment, however, similar cardiovascular hemodynamic measurements were recorded in both positions. Propranolol increased left ventricular end-diastolic volume at rest and at maximal exercise. Left ventricular end-systolic volume, however, was substantially greater only in the upright position both at rest and at maximal exercise when compared with control values. Heart rate, systolic arterial pressure, cardiac index, and pressure volume index were decreased at rest and maximal exercise after treatment with propranolol. Ejection fraction was decreased in the upright position after propranolol administration but was unchanged in the supine position. Handgrip exercise primarily increased heart rate and arterial pressure and did not affect cardiac volume, and this response was unaffected by propranolol.

Effect of dipyridamole and aspirin on late vein-graft patency after coronary bypass operations

To study the prevention of occlusion of aortocoronary-artery bypass grafts, we concluded a prospective, randomized, double-blind trial comparing long-term administration of dipyridamole (begun two days before operation) plus aspirin (begun seven hours after operation) with placebo in 407 patients. Results at one month showed a reduction in the rate of graft occlusion in patients receiving dipyridamole and aspirin. At vein-graft angiography performed in 343 patients (84 per cent) 11 to 18 months (median, 12 months) after operation, 11 per cent of 478 vein-graft distal anastomoses were occluded in the treated group, and 25 per cent of 486 were occluded in the placebo group. The proportion of patients with one or more distal anastomoses occluded was 22 per cent of 171 patients in the treated group and 47 per cent of 172 in the placebo group. All grafts were patent within a month of operation in 94 patients in the placebo group and 116 patients in the treated group; late development of occlusions was reduced from 27 per cent in the placebo group to 16 per cent in the treatment group. The results show that dipyridamole and aspirin continue to be effective in preventing vein-graft occlusion late after operation, and we believe that such treatment should be continued for at least one year.