Effect of the oral hypoglycaemic sulphonylurea glibenclamide, a blocker of ATP-sensitive potassium channels, on walking distance in patients with intermittent claudication

AIMS

The oral hypoglycaemic sulphonylurea glibenclamide stimulates endogenous insulin secretion through blockade of ATP-sensitive potassium (KATP) channels on pancreatic beta cells, but also blocks cardiovascular KATP channels, leading to increased peripheral vascular resistance and reduced peripheral blood flow in non-diabetic subjects. Therefore, this study examined whether a single oral dose of glibenclamide adversely affected the pain-free or maximal walking distance in patients with intermittent claudication.

METHODS

In a double-blind, randomized crossover study, 12 non-diabetic patients with intermittent claudication were given a single oral dose of glibenclamide (5.25 mg) or placebo separated by a washout period of 1 week. A treadmill test was carried out 180 min after glibenclamide/placebo intake for determination of pain-free and maximal walking distance. Plasma glucose concentrations were kept constant by an euglycemic clamp. Changes in ankle/brachial blood pressure index (ABI), serum insulin, and serum glibenclamide were also assessed.

RESULTS

The pain-free walking distance was 62.8 +/- 9.8 metres (mean +/- sem) after glibenclamide and 52.6 +/- 5.9 metres after placebo (P = 0.52). The maximal walking distance was 142.7 +/- 18.7 metres after glibenclamide and 132.6 +/- 16.6 metres after placebo (P = 0.23). The ABI was not significantly changed by glibenclamide compared with placebo. Serum glibenclamide was 0.51 +/- 0.08 microm 180 min after administration of the drug. Glibenclamide produced an 8-fold increase in circulating insulin compared with placebo (P < 0.001).

CONCLUSIONS

Glibenclamide given as a single oral dose commonly used in glucose-lowering drug therapy does not reduce pain-free or maximal walking distance in non-diabetic patients with intermittent claudication.

Myocardial infarction centres: the way forward

In the era of primary PCI, a strategy of admitting patients to the nearest hospital should be obsolete. Instead, a prehospital diagnostic strategy should be implemented in order to: (1) refer patients directly to interventional centres, thereby eliminating delay at local hospitals; (2) alert the interventional centre, thereby reducing door to balloon times; (3) initiate adjunctive medication in the prehospital phase.

Survival trends among Danish patients undergoing coronary angiography for known or suspected ischaemic heart disease: a population based follow up study, 1992-2000

OBJECTIVE

To determine, from population based clinical data, changes in the survival of Danish patients examined by coronary angiography for known or suspected ischaemic heart disease (IHD) during the 1990s.

DESIGN

Follow up study.

SETTING

The departments of cardiology at Rigshospitalet, Copenhagen University Hospital, and Skejby Hospital, Aarhus University Hospital, Denmark.

PATIENTS

Patients with IHD (n = 7021) who underwent first time coronary angiography in 1992, 1996, or 2000.

MAIN OUTCOMES MEASURES

Three year survival was compared between cohorts and with that of the general population. Cox proportional hazards regression was used to estimate mortality ratios adjusted for differences in patient characteristics.

RESULTS

Survival improved substantially--for example, adjusted mortality ratio was 0.69 (95% confidence interval (CI) 0.55 to 0.87) when comparing patients from 2000 with patients from 1992. The absolute standardised survival rates after three years of follow up were 87.1% (95% CI 85.4% to 88.8%), 89.9% (95% CI 88.5% to 91.3%), and 91.2% (95% CI 90.3% to 92.1%) among patients examined in 1992, 1996, and 2000, respectively. The improvement was not explained by the improvement in overall survival in the general population during the study period.

CONCLUSIONS

The survival of Danish patients with known or suspected IHD appears to have improved substantially during the 1990s.

Percutaneous coronary intervention in diabetic patients: a problem?

Pharmacological and technological advances in surgical and interventional coronary treatment modalities have shown reduced cardiovascular mortality in non-diabetic patients, but diabetic patients have not gained the same benefit of invasive treatment as non-diabetics. Although early studies suggest a poorer outcome after angioplasty than after coronary by-pass grafting (CABG) in diabetic patients, more recent studies including improved pharmacological therapy and stent implantation seem to justify increased use of revascularization by percutaneous coronary intervention (PCI) in diabetics with stable and unstable coronary syndromes as the relative benefit in long-term survival, non-fatal myocardial infarction and cerebrovascular accidents is similar. However, diabetic patients are still subject to higher morbidity and mortality after revascularization with CABG and PCI. This is related to increased co-morbidity, metabolic dysregulation, difficulties in obtaining complete revascularization, and more frequent appearance of new lesions as well as restenosis and hemostatic abnormalities. Drug-eluting stents appear to reduce the risk of restenosis, and aggressive antithrombotics also tend to improve the outcome. Unsolved problems are the significance of incomplete revascularization and whether a PCI strategy is associated with a procedure induced progression of the native diabetic vascular disease in treated or untreated vessels. Trials addressing adjunctive treatment and long-term clinical outcome specifically in diabetic patients should clarify these questions.

Ischaemic preconditioning does not protect the heart in obese and lean animal models of type 2 diabetes

AIMS/HYPOTHESIS

The prevalence of type 2 diabetes mellitus is increasing worldwide with obese diabetic patients constituting the majority of this population. Type 2 diabetes is associated with increased morbidity and mortality after acute myocardial infarction. Previous experimental studies of ischaemia-reperfusion tolerance in diabetes have only been performed in animal models of type 1 diabetes mellitus, yielding conflicting data. The aim of the present study was to characterise and compare the tolerance to ischaemia and effects of ischaemic preconditioning (IPC) in hearts from obese Zucker diabetic fatty (ZDF) and lean Goto-Kakizaki (GK) type 2 diabetic rats, using non-obese Zucker and Wistar rats as respective controls.

METHODS

The two rat strains were divided into 8 groups. The ZDF study (n=47) consisted of: Control -IPC, Control +IPC, ZDF -IPC and ZDF +IPC. The GK study (n=38) consisted of: Control -IPC, Control +IPC, GK -IPC and GK +IPC. Hearts, which were studied in a Langendorff preparation perfused with Krebs-Henseleit buffer, were subjected or not to IPC (+IPC, -IPC) before 50 minutes of regional ischaemia and 120 minutes reperfusion.

RESULTS

Ischaemic reperfusion injury was smaller in obese (p<0.05) and lean (p<0.05) type 2 diabetic animals than in their respective control animals. IPC reduced ischaemic reperfusion injury during reperfusion in non-diabetic control rats (p<0.01), but failed to protect hearts from both diabetic animal models. Post-ischaemic haemodynamic recovery was impaired in the ZDF rats compared to both control and GK rats (p<0.05).

CONCLUSIONS/INTERPRETATION

Ischaemic preconditioning does not protect hearts from obese or lean type 2 diabetic animals. However, the susceptibility of the type 2 diabetic myocardium to ischaemic damage is lower than in non-diabetic hearts. The method described here could be used as a tool to study the pathogenesis of increased cardiovascular morbidity and mortality in type 2 diabetes.

Are we underestimating the full potential of early thrombolytic treatment in patients with acute myocardial infarction?

Use of the Boersma curve in order to describe the beneficial effect of thrombolytic treatment at different treatment delays seems questionable, because the curve may underestimate the favourable prognostic effects of early thrombolysis in patients with acute myocardial infarction

Telemedicine used for remote prehospital diagnosing in patients suspected of acute myocardial infarction

INTRODUCTION

In patients with acute myocardial infarction (AMI), considerable time elapses from symptom onset until initiation of thrombolytic therapy or primary percutaneous coronary intervention. Prehospital diagnosing can reduce time delays, and remote diagnosing using telemedicine may be appropriate in areas and countries where ambulances are not staffed with physicians.

OBJECTIVES

To evaluate whether it was technically feasible for physicians at a remote university hospital to diagnose ST-segment-elevation-AMI (AMI(STelev)) in patients suspected of AMI, who were transported by ambulances to a local hospital. To determine associated prehospital delays and in-hospital treatment delays.

METHODS

Patients carried in telemetry equipped ambulances had 12-lead electrocardiograms (ECGs) acquired as soon as possible. En route to the local hospital the ECGs were transmitted to a remote university hospital, by use of the GSM-system. The physician on call at the university hospital interviewed the patients, who were provided with cellular phone headsets, and alerted the local hospital if signs of AMI(STelev), bundle-branch-block-AMI or malignant arrhythmia were detected. Patients transported by traditional ambulances were included in a prospective control group.

RESULTS

In 214 (86%) of 250 patients prehospital diagnosing was successful. Geographically related transmission problems were the primary reason for failure. Ninety-eight per cent of transmitted electrocardiograms and obtained history takings were technically acceptable for diagnostic purposes. Door-to-needle times were shorter amongst patients with AMI(STelev) who were subjected to prehospital diagnosing (n = 13) as compared with patients transported by traditional ambulances (n = 14) (38 vs. 81 min) (P = 0.004).

CONCLUSIONS

It was technically feasible to use telemedicine for remote prehospital diagnosing of patients suspected of AMI. Patients subjected to prehospital diagnosing had shorter door-to-needle times compared with a prospective control group.

The effect of litter size and day of lactation on amino acid uptake by the porcine mammary glands

Twelve multiparous sows (PIC Camborough 15; parity >2) were used to investigate the relationship between litter size and day of lactation, and plasma amino acid (AA) arteriovenous differences (A-VD), AA uptake, and plasma flow across the mammary glands. Sows were assigned randomly to one of the following litter sizes: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 pigs per litter by cross fostering on d 2 postpartum. All sows were surgically fitted with catheters in the carotid artery and the main mammary vein. Matched arteriovenous blood samples were obtained on d 9, 12, 15, 18, 21, and 24 postpartum. Daily mammary uptake of AA was based on the product of plasma A-VD and daily mammary plasma flow (MPF). Daily MPF was estimated using the Fick method based on lysine conservation across the gland, and daily milk production. For the majority of AA, as litter size increased, A-VD did not increase, except for alanine (P < 0.05, linear and quadratic) and valine (P < 0.1; trend; linear and quadratic). As day of lactation increased, A-VD for the majority of AA increased (P < 0.05, linear and quadratic) except for arginine, lysine, and phenylalanine. As litter size increased, net daily mammary AA uptake increased for all indispensable AA (P = 0.001 to P < 0.05, linear and quadratic), excepting arginine. Milk production increased with increasing litter size (P < 0.001, linear) and with increasing day of lactation (P < 0.05, quadratic). Daily MPF increased (P < 0.05, linear) with increasing litter size, but did not change during the period measured from d 9 to 24. In conclusion, litter size appears to be a major determinant of net mammary AA uptake with daily mammary plasma flow a driving variable, whereas AA A-VD is a function of day of lactation and a major variable in determining net AA uptake with advancement of lactation.

Serial magnetic resonance imaging of global and regional left ventricular remodeling during 1 year after acute myocardial infarction

Biplane long-axis cine MRI was performed in 51 patients 1, 13, 26, and 52 weeks after their first AMI. LV mass index (LVMI) was significantly increased 1 week after AMI (84.3 +/- 16.9 vs. 68.1 +/- 11.4 g/m(2) controls, n = 48, p < 0.001), presumably owing to edema of the infarcted myocardium. Six months after AMI, LVMI decreased to 76.5 +/- 16.4 g/m(2), but had again augmented after 1 year (81.8 +/- 17.3 g/m(2), p < 0.05), suggesting late, compensatory left ventricular hypertrophy. In patients treated with primary percutaneous transluminal coronary angioplasty, LVMI decreased 5% over 1 year, while LVMI increased 10% in patients receiving thrombolysis (p < 0.05). In the entire population, the global increase in LVMI 1 year after AMI seemed to reflect global cavity dilatation with unchanged thickness of the vital myocardium. In conclusion, in patients receiving contemporary treatment, LV remodeling only partially complied with the classical patho-anatomical concept.

Prediction of reversible myocardial dysfunction by positron emission tomography, low-dose dobutamine echocardiography, resting ECG, and exercise testing

We studied different algorithms to identify patients with heart failure who could potentially benefit from revascularization. Thirty-five coronary artery bypass (graft) patients with an ejection fraction of 35 +/- 7% underwent preoperative 18F-fluoro-2-deoxyglucose positron emission tomography (PET), low-dose dobutamine echocardiography (LDDE), and exercise testing. Follow-up by echocardiography and coronary angiography was performed 6 months after coronary artery bypass grafting. The sensitivity for prediction of reversible myocardial dysfunction was highest for PET and for ST depression or angina pectoris during exercise testing (100 and 93%, p = NS), 71% for LDDE (p < 0.05 vs. PET), and 50% for resting ECG (p < 0.02 vs. PET and exercise test). The specificity did not differ between LDDE (81%), PET (67%), and resting ECG (71%), but was lowest for exercise testing (33%; p < 0.02 vs. PET, LDDE, and resting ECG). Accuracies were: PET 80%, LDDE 77%, exercise testing 62%, and resting ECG 58% (p < 0.05 vs. PET). In patients with a negative exercise test, recovery was unlikely, and further viability testing may not be needed. In patients with a positive test, recovery may occur, and additional PET or LDDE should be performed. In these cases, PET with an 18F-fluoro-deoxyglucose uptake of > or =70% as the criterion for viability yields optimum diagnostic characteristics. This strategy awaits further evaluation in larger patient populations with heart failure.

[Spontaneous dissection of the left main coronary arteries in three women]

Spontaneous dissection of the coronary artery is a rare cause of sudden death and myocardial infarction. We report three cases in women aged 32, 38, and 55 years. One patient was one week post partum. In one case all three coronary arteries were involved. Two patients underwent coronary artery bypass grafting and one died of acute heart failure. The epidemiology, aetiology, and clinical manifestations are briefly described. We suggest that coronary angiography should be considered in young women with acute myocardial infarction and few risk factors of atherosclerosis.

Biplane long-axis magnetic resonance imaging. Survey projections for rapid estimation of left ventricular mass and global function

OBJECTIVE

To evaluate the accuracy and precision of biplane long-axis magnetic resonance imaging (MRI) and two-dimensional (2D)-echocardiography, for the assessment of left ventricular (LV) mass and volumes, with multislice short-axis MRI as reference standard.

DESIGN

Forty-five cardiac patients and four volunteers with varying LV dilatation and hypertrophy were examined by biplane long-axis gradient-echo MRI, 2D-echocardiography, and multiple short-axis gradient-echo MRI.

RESULTS

Compared with multislice MRI, the accuracy, i.e. the coefficient of variation (c.v.) of inter-method differences of measured variables, was median 15.7% for biplane MRI and 18.5% for 2D-echocardiography. The precision, expressed as the c.v. of repeated measurements, was median 8.5% for multislice MRI, 9.5% for biplane MRI and 12.4% for 2D-echocardiography. For the determination of LV mass index, MRI was significantly more precise (c.v.: 6.0-8.4%) than 2D-echocardiography (c.v.: 13.7-14.3%, p < 0.05).

CONCLUSION

Biplane long-axis MRI is a fast and simplified method, offering the advantage of displaying anatomy and function in recognizable projections. For the estimation of LV mass and volumes, biplane MRI had an acceptable accuracy, and a precision that did not differ significantly from that of multislice MRI.

Influence of nitric oxide synthase and adrenergic inhibition on adenosine-induced myocardial hyperemia

BACKGROUND

Myocardial perfusion during adenosine-induced hyperemia is used both in clinical diagnosis of coronary heart disease and for scientific investigations of the myocardial microcirculation. The objective of this study was to clarify whether adenosine-induced hyperemia is dependent on endothelial NO production or is influenced by adrenergic mechanisms.

METHODS AND RESULTS

In 12 healthy men, myocardial perfusion was measured with PET in 2 protocols performed in random order, each including 3 perfusion measurements. First, perfusion was measured at rest. Second, either saline or the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 4 mg/kg) was infused, and perfusion during adenosine-induced hyperemia was determined. Last, in both protocols, the alpha-receptor blocker phentolamine was infused, and perfusion during adenosine-induced hyperemia was determined again. Resting perfusion was similar in the 2 protocols (0.69+/-0.14 and 0.66+/-0.18 mL. min(-1). g(-1)). L-NAME increased mean arterial blood pressure by 12+/-7 mm Hg (P<0.01) and reduced heart rate by 16+/-7 bpm (P<0.01). Adenosine-induced hyperemia (1.90+/-0.33 mL. min(-1). g(-1)) was attenuated by L-NAME (1.50+/-0.55 mL. min(-1). g(-1), P<0.01). The addition of phentolamine had no effect on the adenosine-induced hyperemia (2.10+/-0.34 mL. min(-1). g(-1), P=NS). In the presence of L-NAME, however, when the adenosine response was attenuated, phentolamine was able to increase hyperemic perfusion (2.05+/-0.44 mL. min(-1). g(-1), P<0.05).

CONCLUSIONS

Inhibition of endogenous NO synthesis attenuates myocardial perfusion during adenosine-induced hyperemia, indicating that coronary vasodilation by adenosine is partly endothelium dependent. alpha-Adrenergic blockade has no effect on adenosine-induced hyperemia unless NO synthesis is inhibited.

Magnetic resonance imaging seems safe in patients with intracoronary stents

We elucidated whether exposure to cardiac magnetic resonance imaging (MRI) of patients with implanted intracoronary stents is associated with increased risk of stent-thrombosis, stent-restenosis, or other cardiovascular complications. Forty-seven patients admitted with acute myocardial infarction (AMI) were studied. Twenty-three were included in a serial cardiac MRI study, using 1.5-T scanners with standard gradient systems. The remaining patients were control subjects who were matched for age and gender with the MRI group. All patient had intracoronary stents implanted in connection with primary angioplastic treatment (PTCA) of AMI (n = 21), secondary PTCA procedures due to recurrent angina (n = 22), or both (n = 4). In the MRI group (n = 23, aged 58 +/- 10 yr), MRI was carried out one to five times in each patient a median of 166 days (range, 1-501) after stent implantation. The control group comprised 24 patients, ages 59 +/- 11 yr. The incidences of stent-thrombosis, stent-restenosis, and other cardiovascular complications did not differ statistically significantly between the two groups. In the MRI group, stent-related thrombosis (n = 1) or restenosis (n = 7) was observed in eight cases a median of 102 days (range, 7-547) after MR examination and a median of 318 days (range, 138-713) after stent implantation, compared with nine cases in the control group (thrombosis, n = 1; restenosis, n = 8) observed a median of 147 days (range, 1-267) after stent implantation. No acute thromboembolic or other complication occurred in immediate connection with MRI. The follow-up time was 21.3 +/- 4.5 months. This small study shows no evidence of an MRI-related risk of stent-restenosis or other cardiovascular complications, not even if cardiac MRI is performed early after stent implantation.

99mTc-Sestamibi SPECT is a useful technique for viability detection: results of a comparison with NH3/FDG PET

OBJECTIVE

Assessment of myocardial viability by 99mTc-Sestamibi Single Photon Emission Computerized Tomography (SPECT) has been suggested as a more readily available and cheaper alternative to Positron Emission Tomography (PET) with 13N-ammonia (NH3) and 18F-fluoro-deoxy-glucose (FDG). We hypothesized that a semi-quantitative evaluation by SPECT could delineate myocardial viability with an acceptable concordance to PET.

DESIGN

Fifty patients (age 57+/-7 years; ejection fraction 28 +/- 8%), with ischemic cardiomyopathy, underwent SPECT and PET imaging in random order. Viability by SPECT was defined as a defect size <50% of the segment area, or a defect representing > or =50% of the segment but with a mean activity > or =50% of peak activity. PET viability was defined as a perfusion score >2 and FDG score < or =2 (five-point scale, 0 = normal, 4 = absent activity).

RESULTS

By segmental comparison to PET. SPECT yielded a sensitivity and specificity of 87% and 82% for detection of viable myocardium. The positive and negative predictive values were 96% and 58%, respectively.

CONCLUSION

In patients with severe ischemic cardiomyopathy 99mTc-Sestamibi SPECT can delineate viable myocardium with an acceptable segmental concordance to NH3/FDG PET.

Standardized ileal protein and amino acid digestibility by growing pigs and sows

Experiments were conducted to determine the effect of the physiological condition of swine on standardized ileal digestibility coefficients (SID). The apparent ileal digestibility coefficients were determined for crude protein and amino acids in six feed ingredients (corn, barley, wheat, soybean meal, canola meal, and meat and bone meal) in growing pigs and in gestating and lactating sows. Growing pigs and lactating sows were given free access to their diets, whereas gestating sows were allowed to consume only 2 kg of feed daily. The nonspecific (basal) endogenous losses of protein and amino acids were determined under similar feeding regimens after feeding a protein-free diet. The SID for crude protein and amino acids were calculated by correcting the apparent ileal digestibility coefficients for the nonspecific endogenous losses of protein and amino acids. With a few exceptions, there were no differences (P > 0.05) in the SID for crude protein and amino acids between growing pigs and lactating sows. Overall, gestating sows had higher (P < 0.05) SID for crude protein and all amino acids, except for tryptophan and aspartate, compared with growing pigs. Likewise, the SID of most amino acids obtained by gestating sows were higher (P < 0.05) than those obtained by lactating sows. Interactions (P < 0.05) between animals and diets were observed for gestating sows compared with growing pigs as well as gestating sows compared with lactating sows. As a consequence, it is not possible to extrapolate data from one feed ingredient to another. On most occasions, the lowest SID among the indispensable amino acids was calculated for threonine, valine, and lysine. It is concluded that gestating sows fed 2 kg of feed per day have higher standardized digestibility coefficients than do growing pigs and lactating sows given free access to their diets. This difference may be due to differences in daily feed intake rather than to the physiological status of the animals.

Time course of vascular remodeling, formation of neointima and formation of neoadventitia after angioplasty in a porcine model

BACKGROUND

Vascular remodeling is the major cause of restenosis after coronary balloon angioplasty but the pathophysiology of this process is not known.

OBJECTIVE

To examine the time courses of vascular remodeling, formation of neointima and adventitial changes after coronary angioplasty.

DESIGN

An experimental study on pigs using coronary angiography, intravascular ultrasound (IVUS), and histology.

METHODS

Deep vessel-wall injury was induced by conventional balloon angioplasty in the circumflex and right coronary arteries, and by retraction of a chain-encircled balloon in the left anterior descending artery. Angiography in all three arteries and IVUS measurements in circumflex and left anterior descending arteries were performed before and after angioplasty, and at follow-up on days 0, 1, 4, 7, 14, 28, and 56 (n = 5 in each group). Serial IVUS measurements were used to determine vascular remodeling. Formation of neointima and neoadventitia was measured by histomorphometry.

RESULTS

Angiographically evident loss of lumen and ultrasonographically detectable constrictive remodeling occurred between day 7 and day 28. IVUS measurements showed that late loss of lumen (days 28 and 56) was correlated to vascular remodeling but not to the increase in wall area (neointima plus media). Histomorphometry revealed that neointima was present from day 7 and that amount of neointima increased up to day 28. Area of adventitia increased during the first 4 days and remained unchanged thereafter. Adventitial neovascularization by vasa vasorum was observed from day 4 onward.

CONCLUSIONS

Formation of neoadventitia precedes late loss of lumen, constrictive remodeling, and formation of neointima. The time course of vascular remodeling coincides with growth of neointima rather than with changes in the adventitia.

Captopril improves oxygen and glucose extraction in pig hearts during reperfusion after cold cardioplegic storage

The purpose of this study was to evaluate the haemodynamic and metabolic effects of captopril during reperfusion of pig hearts following 360 min global hypothermic cardioplegia and storage (HCS). The hearts were perfused with one litre of cold crystalloid cardioplegia (Bretschneider solution no. 3), excised and stored in saline at 4 degrees C for 360 min. The hearts were then reperfused with blood in a modified Langendorff model for 60 min. Left ventricular function, myocardial blood flow, and arteriovenous differences in oxygen, glucose and lactate were monitored intraoperatively and during reperfusion. Two groups of hearts were studied. Group I (captopril treated, n = 9): the pigs were pre-medicated with increasing oral doses of captopril for 3 weeks (12.5 mg-150 mg daily) and an intravenous dose (25 mg) upon arrival at the laboratory. Captopril was added to the cardioplegia (1000 microg/l) and to the reperfusion media (1000 microg/l). Group II (controls, n = 8): the pigs were given no premedication, captopril-free cardioplegia and the hearts were reperfused with captopril-free blood. Captopril increased myocardial oxygen and glucose extraction during reperfusion (p < 0.05 for both) while lactate remained unchanged after 360 min HCS. Treatments with captopril increased developed left ventricular pressure (DLVP) and relaxation (-dP/dtmax) during reperfusion (p < 0.05 for both), while contractility (+dP/dtmax) was unchanged. Heart rate was reduced in captopril-treated hearts (p < 0.05) while myocardial blood flow (MBF) was similar in the two groups. Captopril administration prior to and during HCS and postcardioplegic reperfusion improves oxygen and glucose extraction in large spontaneously beating porcine hearts during reperfusion. The underlying mechanisms seem to involve metabolic modulation, since myocardial uptake of oxygen and glucose was increased in the absence of changes in myocardial blood flow.

Peripheral flow response to transient arterial forearm occlusion does not reflect myocardial perfusion reserve

BACKGROUND

Ultrasonographic evaluation of systemic arterial function is widely available, and a close relation of endothelial function in the coronary and brachial arteries has been documented. It is unknown, however, whether a similar correlation exists for their 2 microcirculatory territories and thus whether assessment of the systemic microcirculation can be used similarly as a surrogate marker of myocardial perfusion.

METHODS AND RESULTS

Twenty-three patients with documented coronary artery disease (CAD; 66+/-9 years old, 18 men), 16 patients with syndrome X (SX; 56+/-5 years old, 13 women), and 45 healthy control subjects (C; 34+/-9 years old, 22 men) were studied. Myocardial perfusion was measured at rest and after dipyridamole (0.56 mg. kg(-1). min(-1) over 4 minutes) by PET, and brachial artery blood flow was measured at rest and after transient forearm ischemia by standard Doppler ultrasound techniques. Dipyridamole increased myocardial perfusion in all groups (mL. g(-1). min(-1): CAD, 0.89+/-0.27 versus 1.62+/-0.67, P:<0.001; SX, 0.82+/-0.16 versus 1.67+/-0.49, P:<0.001; and C, 0.82+/-0.15 versus 2.32+/-0.64, P:<0.001). Postocclusion forearm flow increased similarly in all groups (CAD, 52+/-18 versus 174+/-77 mL/min, P:<0.001; SX, 49+/-29 versus 202+/-82 mL/min, P:<0.001; and C, 61+/-34 versus 229+/-108 mL/min, P:<0.001). No significant correlations were found between peripheral and myocardial microcirculatory beds for either resting flow, hyperemic flow, or flow reserve in any of the groups (r(2)<0.1, P:=NS).

CONCLUSIONS

The peripheral perfusion responses to transient forearm ischemia do not correlate with dipyridamole-induced myocardial hyperemia. The lack of correlation indicates different mechanisms of microvascular activation or regulation and confirms that extrapolations between findings in the 2 vascular beds are not suitable.

Histopathologic validation of in-vivo angioscopic observation of coronary thrombus after angioplasty in a porcine model

BACKGROUND

Coronary angioscopy has been reported to be superior to angiography and intravascular ultrasound for detecting intracoronary thrombus. However, in-vivo histopathologic validation of angioscopic detection of intracoronary thrombus had not been performed.

OBJECTIVE

To perform histopathologic validation of in-vivo angioscopic detection of coronary thrombus.

DESIGN

An experimental, blinded comparison of angioscopy and histopathology.

METHODS

Coronary angioscopy was performed from 0 to 14 days after angioplasty in 39 porcine coronary arteries. When thrombus was detected by angioscopy, it was subclassified into white, mixed red-white, or red thrombus according to color. By histopathology the presence of thrombus was determined and subclassified into platelet-rich, mixed platelet-erythrocyte, or erythrocyte-rich thrombus.

RESULTS

Angioscopy correctly classified 19 of 21 coronary thrombi (sensitivity 90%) but incorrectly classified nine of 18 arteries without formation of thrombus as having a thrombus (specificity 50%). Positive and negative predictive values were 68 and 82%, respectively. The angioscopic subclassification of thrombus into white, mixed red-white, or red thrombi was not correlated to the corresponding histopathologic morphology (platelet-rich, mixed platelet-erythrocyte, or erythrocyte-rich) of the observed thrombi (chi2 test: P = 0.5).

CONCLUSIONS

Angioscopic detection of thrombus in vivo had high sensitivity and negative predictive value but low-to-moderate specificity and positive predictive value. Visual assessment of color of angioscopically detected thrombi seemed not to reflect histopathologic morphology of thrombus according to the definitions used in the present study.

Energy stores and metabolites in chronic reversibly and irreversibly dysfunctional myocardium in humans

OBJECTIVES

Our goal was to study metabolic energy stores and lactate content in chronic reversibly and irreversibly dysfunctional myocardium.

BACKGROUND

It is unknown whether metabolism is deranged in chronic reversibly and irreversibly dysfunctional myocardium in humans. Semiquantitative histological examinations have shown altered mitochondrial morphology and glycogen accumulation in dysfunctional regions.

METHODS

We studied 25 patients with a mean ejection fraction of 38 +/- 9% scheduled for coronary artery bypass surgery. Regional perfusion and metabolism were assessed by positron emission tomography, and regional function was assessed by echocardiography. Perioperative myocardial biopsies were obtained from a control region and from a dysfunctional region. We analyzed biopsies for contents of noncollagen protein (NCP), ATP, ADP, AMP, glycogen and lactate. Six months after surgery we assessed wall motion by echocardiography to group patients in those with (n = 11) and without (n = 14) functional improvement.

RESULTS

Reversibly dysfunctional myocardium had reduced perfusion (0.59 +/- 0.16 vs. 0.69 +/- 0.20 ml/g/min, p < 0.05), similar glucose-tracer uptake (92 +/- 12 and 95 +/- 14%), ATP/ADP ratio (2.4 +/- 1.1 and 2.4 +/- 0.7), glycogen content (631 +/- 174 and 632 +/- 148 nmol/microg NCP) and lactate levels (59 +/- 27 and 52 +/- 29 nmol/microg NCP) compared with control regions. Irreversibly dysfunctional regions (n = 14) had severely reduced perfusion (0.48 +/- 0.15 vs. 0.72 +/- 0.12 ml/g/min, p < 0.001) and glucose-tracer uptake (52 +/- 16 vs. 94 +/- 15%, p < 0.001), reduced ATP/ADP ratio (1.5 +/- 0.9 vs. 2.3 +/- 0.9, p < 0.05), similar glycogen content (579 +/- 265 vs. 593 +/- 127 nmol/microg NCP) and increased lactate levels (114 +/- 52 vs. 89 +/- 24 nmol/microg NCP, p < 0.01) compared with control regions.

CONCLUSIONS

Contents of metabolic energy stores and lactate in chronic reversibly dysfunctional myocardium were preserved. In contrast, energy stores were depleted in myocardium without functional recovery after revascularization.

Positron emission tomography and low-dose dobutamine echocardiography in the prediction of postrevascularization improvement in left ventricular function and exercise parameters

BACKGROUND

We studied the value of low-dose dobutamine echocardiography (LDDE) and positron emission tomography (PET) in predicting improvement of left ventricular function and exercise parameters after revascularization.

METHODS

Forty-six consecutive patients with ischemic heart disease and an ejection fraction (EF) of 35% +/- 7% were included. Before revascularization, the patients underwent exercise testing and myocardial viability testing by LDDE and fluoride 18-fluoro-2-deoxyglucose PET. Six months after revascularization they underwent coronary angiography to study graft patency, and echocardiographic examination and the exercise test were repeated.

RESULTS

In the prediction of the presence or absence of improved postrevascularization function in left ventricular regions with patent grafts, PET was more sensitive than LDDE (42/52 regions [81%] vs 27/52 regions [51%], P <.01), whereas LDDE was more specific than PET (187/209 regions [89%] vs 118/209 regions [56%], P <.001). Improvement of regional myocardial dysfunction was found in 19 patients, but their global left ventricular function did not improve significantly (EF 34% +/- 6% and 36% +/- 7%). In the remaining 27 patients with irreversible dysfunction, EF decreased (EF 36% +/- 7% vs 32% +/- 8%, P <.05). Among patients with reversible myocardial dysfunction, the rate pressure product (RPP) increased after revascularization (19,522 +/- 5474 vs 26,190 +/- 5610 mm Hg/min, P <.01), whereas the RPP did not change in patients with irreversible myocardial dysfunction (21,546 +/- 5450 and 22,774 +/- 8249 mm Hg/min). The number of PET viable segments was a predictor of the postoperative increase in the RPP in univariate (P <.04) and multivariate analyses (P <.001). In contrast, LDDE did not bear any prognostic information about improvement in the RPP.

CONCLUSIONS

This study confirms earlier findings of higher sensitivity and lower specificity of PET compared with LDDE in predicting improvement of regional left ventricular function after revascularization. However, the feasibility of predicting postrevascularization improvement of exercise parameters seems unique for PET. The potential prognostic value of this finding needs further investigation.