Improvement in the diagnosis of abscesses associated with endocarditis by transesophageal echocardiography

BACKGROUND

Echocardiography is recognized as the method of choice for the noninvasive detection of valvular vegetations in patients with infective endocarditis, with transesophageal echocardiography being more accurate than transthoracic echocardiography. The diagnosis of associated abscesses by transthoracic echocardiography is difficult or even impossible in many cases, however, and it is not known whether transesophageal echocardiography is any better.

METHODS

To determine the value of transesophageal echocardiography in the detection of abscesses associated with endocarditis, we studied prospectively by two-dimensional transthoracic and transesophageal echocardiography 118 consecutive patients with infective endocarditis of 137 native or prosthetic valves that was documented during surgery or at autopsy.

RESULTS

During surgery or at autopsy, 44 patients (37.3 percent) had a total of 46 definite regions of abscess. Abscesses were more frequent in aortic-valve endocarditis than in infections of other valves, and the infecting organism was more often staphylococcus (52.3 percent of cases) in patients with abscesses than in those without abscesses (16.2 percent). The hospital mortality rate was 22.7 percent in patients with abscesses, as compared with 13.5 percent in patients without abscesses. Whereas transthoracic echocardiography identified only 13 of the 46 areas of abscess, the transesophageal approach allowed the detection of 40 regions (P less than 0.001). Sensitivity and specificity for the detection of abscesses associated with endocarditis were 28.3 and 98.6 percent, respectively, for transthoracic echocardiography and 87.0 and 94.6 percent for transesophageal echocardiography; positive and negative predictive values were 92.9 and 68.9 percent, respectively, for the transthoracic approach and 90.9 and 92.1 percent for the transesophageal approach. Variation between observers was 3.4 percent for transthoracic and 4.2 percent for transesophageal echocardiography.

CONCLUSIONS

The data indicate that transesophageal echocardiography leads to a significant improvement in the diagnosis of abscesses associated with endocarditis. The technique facilitates the identification of patients with endocarditis who have an increased risk of death and permits earlier treatment.

Echocardiography in infective endocarditis: reassessment of prognostic implications of vegetation size determined by the transthoracic and the transesophageal approach

In 105 patients with active infective endocarditis, disease-associated complications defined as severe heart failure (New York Heart Association class IV), embolic events and in-hospital death were correlated to the vegetation size determined by both transthoracic and transesophageal echocardiography. A detailed comparison between anatomic and echocardiographic findings, performed in a subgroup of 80 patients undergoing surgery or necropsy, revealed that true valvular vegetations can be reliably identified by echocardiography in the vast majority of patients; the detection rate was significantly higher for the transesophageal (90%) than for the transthoracic (58%) approach, particularly when infected prosthetic valves were evaluated. However, an accurate echocardiographic differentiation between true vegetations and other endocarditis-induced valve destruction (ruptured leaflets or chordae) is impossible. The correlation of vegetation size with endocarditis-associated complications showed that patients with a vegetation diameter greater than 10 mm had a significantly higher incidence of embolic events than did those with a vegetation diameter less than or equal to 10 mm (22 of 47 versus 11 of 58; p less than 0.01). Particularly for patients with mitral valve endocarditis, a vegetation diameter greater than 10 mm was highly sensitive in identifying patients at risk for embolic events. Vegetation size, however, was not significantly different in patients with and without severe heart failure or in patients surviving or dying during acute endocarditis. In addition, no significant correlation was found between vegetation size and location of endocarditis or type of infective organism.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective attenuation of endothelium-mediated vasodilation in atherosclerotic human coronary arteries

This study was undertaken to determine whether atherosclerosis impairs relaxations mediated by endothelium-derived relaxing factor (EDRF) in human coronary arteries. Epicardial coronary arteries were obtained from the hearts of cardiac transplantation patients with or without histologically documented coronary atherosclerosis (atherosclerotic arteries were from patients aged 42-55 years, nonatherosclerotic arteries were from patients aged 14-24 years). Transverse strip preparations were mounted in organ baths for isometric tension recording. Tension was induced with prostaglandins F2 alpha. Indomethacin (10(-5) M) was present to prevent possible interference from endogenously formed prostaglandins. The EDRF-mediated relaxations in response to substance P (10(-10) to 10(-8) M), bradykinin (10(-9) to 10(-7) M), and Ca2+-ionophore A23187 (10(-9) to 10(-7) M) were significantly attenuated in atherosclerotic arteries. In deendothelialized tissues these compounds had no effect. In contrast, endothelium-independent relaxations induced by isoprenaline (10(-7) to 10(-5) M) were not affected by atherosclerosis. Atherosclerotic arteries showed also normal relaxations with high concentrations of glyceryl trinitrate (10(-8) to 10(-7) M), but reduced relaxations with a lower concentration of the compound (10(-9) M). Acetylcholine (10(-7) to 10(-6) M) only produced endothelium-dependent relaxations in 8 of 60 arterial preparations (with or without atherosclerosis). In most of the arteries, it was a direct vasoconstrictor (which may have masked EDRF release in many cases). Omission of indomethacin from the bath solution increased the incidence of moderate acetylcholine-induced relaxations (9 of 16 preparations). It is concluded that atherosclerosis attenuates EDRF-mediated vasospasm and myocardial ischemia.

Release of intact endothelium-derived relaxing factor depends on endothelial superoxide dismutase activity

Endothelium-derived relaxing factor (EDRF) is rapidly inactivated by radicals. Endothelial cells possess several antioxidant defense mechanisms. It is not clear which intrinsic antioxidant defense systems are important to preserve the release of biologically active EDRF. We impaired antioxidant defense in normal vascular tissue by inhibiting catalase activity with 3-amino-1,2,4-triazole (AT), superoxide dismutase with diethyldithiocarbamate (DETC), and by reducing glutathione content via inhibiting glutathione synthesis with L-buthionine-(S,R)-sulfoximine (BSO). Pretreatment of rabbit aorta in vitro with DETC markedly reduced endothelium-dependent relaxation in response to acetylcholine and calcium ionophore A23187 and, to a lesser extent, reduced endothelium-independent relaxation in response to nitroprusside. Pretreatment of cultured bovine aortic endothelial cells (BAEC) with DETC did not alter release of nitrogen oxides (measured by chemiluminescence), but, the effluent of pretreated cells showed marked depression in vasodilator activity (measured by bioassay). Pretreatment of rabbit aorta in vitro with AT did not alter endothelium-dependent and -independent relaxations. Pretreatment of BAEC with BSO did not alter the release of nitrogen oxides or the vasodilator activity. These results suggest that endothelial superoxide dismutase activity, but not catalase or glutathione, is necessary for the release of biologically active EDRF. An imbalance of the intrinsic superoxide dismutase and the production of superoxide anions may therefore predispose to impaired endothelium-dependent relaxations and alter vascular reactivity.

Atrial septal aneurysm in adult patients. A multicenter study using transthoracic and transesophageal echocardiography

BACKGROUND

An atrial septal aneurysm (ASA) is a well-recognized abnormality of uncertain clinical relevance. We reevaluated the clinical significance of ASA in a large series of patients. The aims of the study were to define morphological characteristics of ASA by transesophageal echocardiography (TEE), to define the incidence of ASA-associated abnormalities, and to investigate whether certain morphological characteristics of ASA are different in patients with and without previous events compatible with cardiogenic embolism.

METHODS AND RESULTS

Patients with ASA were enrolled from 11 centers between May 1989 and October 1993. All patients had to undergo transthoracic and transesophageal echocardiography within 24 hours of each other; ASA was defined as a protrusion of the aneurysm > 10 mm beyond the plane of the atrial septum as measured by TEE. Patients with mitral stenosis or prosthesis or after cardiothoracic surgery involving the atrial septum were excluded. Based on these criteria, 195 patients 54.6 +/- 16.0 years old (mean +/- SD) were included in this study. Whereas TEE could visualize the region of the atrial septum and therefore diagnose ASA in all patients, ASA defined by TEE was missed by transthoracic echocardiography in 92 patients (47%). As judged from TEE, ASA involved the entire septum in 100 patients (51%) and was limited to the fossa ovalis in 95 (49%). ASA was an isolated structural defect in 62 patients (32%). In 106 patients (54%), ASA was associated with interatrial shunting (atrial septal defect, n = 38; patent foramen ovale, n = 65; sinus venosus defect, n = 3). In only 2 patients (1%), thrombi attached to the region of the ASA were noted. Prior clinical events compatible with cardiogenic embolism were associated with 87 patients (44%) with ASA; in 21 patients (24%) with prior presumed cardiogenic embolism, no other potential cardiac sources of embolism were present. Length of ASA, extent of bulging, and incidence of spontaneous oscillations were similar in patients with and without previous cardiogenic embolism; however, associated abnormalities such as atrial shunts were significantly more frequent in patients with possible embolism.

CONCLUSIONS

As shown previously, TEE is superior to the transthoracic approach in the diagnosis of ASA. The most common abnormalities associated with ASA are interatrial shunts, in particular patent foramen ovale. In this retrospective study, patients with ASA (especially with shunts) showed a high frequency of previous clinical events compatible with cardiogenic embolism; in a significant subgroup of patients, ASA appears to be the only source of embolism, as judged by TEE. Our data are consistent with the view that ASA is a risk factor for cardiogenic embolism, but thrombi attached to ASA as detected by TEE are apparently rare.

Assessment of left atrial appendage function by biplane transesophageal echocardiography in patients with nonrheumatic atrial fibrillation: identification of a subgroup of patients at increased embolic risk

OBJECTIVES

This study was conducted to identify a subgroup of patients with nonrheumatic atrial fibrillation with an increased risk for cardiogenic embolism by assessing left atrial appendage function.

BACKGROUND

Patients with nonrheumatic atrial fibrillation have an increased risk for thromboembolic complications. The left atrial appendage is the most likely source for thrombus formation. It is likely that the appendage function (contraction, filling dynamics) is related to the pathogenesis of thrombus formation.

METHODS

Twenty-nine patients with nonrheumatic atrial fibrillation (group I) underwent biplane transesophageal echocardiography. The maximal and minimal areas during a cardiac cycle and the peak emptying and filling velocities of the appendage were measured in both scan planes. For comparison, two additional groups were also analyzed. Group II consisted of 12 patients with chronic atrial fibrillation due to significant mitral stenosis, and group III consisted of 30 patients who were in sinus rhythm.

RESULTS

Patients with nonrheumatic atrial fibrillation showed two distinct appendage flow patterns: either well defined peak filling and emptying waves (> or = 25 cm/s) with visible fibrillatory contractions of the appendage wall ("high flow profile") or irregular, very low, peak filling and emptying waves (< 25 cm/s) associated with almost no visible appendage contractions ("low flow profile"). The left atrial appendage function in the first subgroup resembles that seen in patients with sinus rhythm, whereas the appendage function in the latter subgroup resembles more the "static pouch" seen in patients with rheumatic atrial fibrillation. Events suggestive of cardiogenic embolism occurred in six patients from group I, five of whom were in the low flow profile subgroup (p < 0.05). The spontaneous echo contrast phenomenon was observed in 80% of the low flow profile subgroup but in only 5% in the high flow profile subgroup (p < 0.05). Three thrombi confined to the left atrial appendage were detected by transesophageal echocardiography in group I; all three of the patients were in the low flow profile subgroup.

CONCLUSIONS

The assessment of left atrial appendage function by transesophageal echocardiography may be helpful to identify subgroups of patients with nonrheumatic atrial fibrillation with an increased risk of thrombus formation.

Diagnosis of noninfective cardiac mass lesions by two-dimensional echocardiography. Comparison of the transthoracic and transesophageal approaches

This study was conducted in 46 patients with cardiac thrombi, 15 patients with atrial myxomas, and 32 patients with other cardiac or paracardiac tumors. Diagnoses were subsequently proven by surgery, autopsy, computed tomography, magnetic resonance imaging, or angiography in all patients. All patients underwent precordial and transesophageal two-dimensional echocardiography to assess the various mass detection rates. Atrial myxomas and predominantly left-sided cardiac tumors were identified by both echocardiographic techniques with comparable detection rates. Left ventricular apical thrombi were detected more frequently by precordial echocardiography. In contrast, transesophageal echocardiography was superior in visualizing left atrial appendage thrombi, small and flat thrombi in the left atrial cavity, thrombi and tumors in the superior vena cava, and masses attached to the right heart and the descending thoracic aorta. These data indicate that transesophageal echocardiography leads to a clinically relevant improvement of the diagnostic potential in patients in whom cardiac masses are suspected or have to be excluded in order to ensure the safety of clinical procedures.

Angiotensin II-induced superoxide anion generation in human vascular endothelial cells: role of membrane-bound NADH-/NADPH-oxidases

BACKGROUND

Angiotensin II (ANG II) mediated hypertension accelerates atherosclerosis (AS) and thereby increases the incidence of myocardial infarction (MI). On the other hand, superoxide anion (O2-) is involved in the modification of low density lipoproteins, inhibition of prostacyclin (PGI2) formation and breakdown of nitric oxide. These events finally lead to rapid progression of AS and MI. In the present study, we investigate whether ANG II can induce O2- release from human vascular endothelial cells (HVECs) and the possible mechanisms involved.

METHODS AND RESULTS

The expression of ANG receptors subtype-1 (AT-1) and subtype-2 (AT-2) were identified by using reverse transcription polymerase chain reaction and sequence analysis. The O2- production was dose-dependently increased in HVECs treated with ANG II (10(-7)-10(-9) M) and with a maximum rate after 1 h of incubation. This event was significantly inhibited by pretreatment of cells with the specific AT-1 blocker losartan (10(-7) M) and to a lesser extent by the specific AT-2 receptor blocker PD123319 (10(-7) M). The combined incubation of both receptor blockers was even more effective. In addition, our lucigenin-enhanced chemiluminescence assay showed that the activity of plasma membrane-bound NADH-/NADPH-oxidases derived from ANG II-treated cells was also significantly increased, this effect was reduced in cells pretreated with losartan or to lesser extent by PD123319. However, the activity of xanthine oxidase remained unchanged in response to ANG II. Furthermore, the basal O2- release from HVECs was inhibited in cells treated with angiotensin-converting enzyme (ACE) inhibitor, Lisinopril (10(-6) M), and this event could be reversed by ANG II.

CONCLUSION

ANG II induces O2- release in HVECs via activation of membrane-bound NADH-/NADPH-oxidase, an effect, that is mediated by both AT-1 and AT-2 receptors. This suggests that acceleration of AS and MI in ANG II-mediated hypertension may at least be due to ANG II-induced O2- generation from vascular endothelial cells. In this case, the ACE inhibitors and the ANG receptor antagonists may act as causative "antioxidants".

Chronic treatment with polyethylene-glycolated superoxide dismutase partially restores endothelium-dependent vascular relaxations in cholesterol-fed rabbits

The endothelium-derived relaxing factor is rapidly inactivated by superoxide radicals, and atherosclerotic vessels generate excess radical species. We tested the hypothesis that an imbalance between intrinsic superoxide dismutase (SOD) activity and the generation of superoxide radicals in atherosclerotic arteries may result in augmented inactivation of endothelium-derived relaxing factor. Vascular SOD was increased in normal and cholesterol-fed (1% cholesterol for 4 months) rabbits approximately twofold by treatment with polyethylene-glycolated SOD (PEG-SOD; 41,000 units/kg/day i.m.) for 1 week. Aortic rings from these animals and nontreated control and atherosclerotic rabbits subsequently were studied in organ chambers. Endothelium-dependent relaxations to acetylcholine and the calcium ionophore A23187 were improved by PEG-SOD in atherosclerotic but not in normal rabbits. PEG-SOD pretreatment did not alter endothelium-independent relaxations to nitroprusside. Thus, treatment with PEG-SOD can partially restore impaired endothelium-dependent relaxation of atherosclerotic arteries. We conclude that generation of oxygen-derived radicals likely contributes to endothelial dysfunction of atherosclerotic arteries.

Diagnosis of patent foramen ovale by transesophageal echocardiography and association with cerebral and peripheral embolic events

This study compares the value of transthoracic (TTE) and transesophageal (TEE) color Doppler and contrast echocardiography for detecting a patent foramen ovale (PFO). A total of 238 patients were studied: 74 patients with a history of otherwise unexplained ischemic stroke, transient cerebral ischemic attacks or peripheral embolic events (group A), 48 with a history of similar episodes explained by other cardiac abnormalities (group B), and 116 with no embolic events (group C). A PFO was detected by contrast TEE in 50 of 238 patients (21%) compared with 45 patients (19%) by color Doppler TTE. In a subgroup of 198 patients, TEE results could be compared with TTE findings. No patient had a PFO identified by color Doppler TTE. Contrast TTE detected a PFO in 15 patients (8%) compared with contrast TEE which demonstrated a PFO in 44 of 198 patients (22%) (p less than 0.001). Prevalence of PFO by TEE was 22, 21 and 22% in groups A, B and C, respectively. A PFO was present in 50% of patients aged less than 40 years and otherwise unexplained ischemic stroke; this percentage was higher (p less than 0.05) than corresponding values found in all other groups. Thus, contrast and color Doppler TEE are significantly superior to TTE for detecting PFO. The prevalence of PFO is significantly increased in young adults with otherwise unexplained ischemic stroke.

Empagliflozin improves endothelial and cardiomyocyte function in human heart failure with preserved ejection fraction via reduced pro-inflammatory-oxidative pathways and protein kinase Gα oxidation

AIMS

Sodium-glucose-cotransporter-2 inhibitors showed favourable cardiovascular outcomes, but the underlying mechanisms are still elusive. This study investigated the mechanisms of empagliflozin in human and murine heart failure with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

The acute mechanisms of empagliflozin were investigated in human myocardium from patients with HFpEF and murine ZDF obese rats, which were treated in vivo. As shown with immunoblots and ELISA, empagliflozin significantly suppressed increased levels of ICAM-1, VCAM-1, TNF-α, and IL-6 in human and murine HFpEF myocardium and attenuated pathological oxidative parameters (H2O2, 3-nitrotyrosine, GSH, lipid peroxide) in both cardiomyocyte cytosol and mitochondria in addition to improved endothelial vasorelaxation. In HFpEF, we found higher oxidative stress-dependent activation of eNOS leading to PKGIα oxidation. Interestingly, immunofluorescence imaging and electron microscopy revealed that oxidized PKG1α in HFpEF appeared as dimers/polymers localized to the outer-membrane of the cardiomyocyte. Empagliflozin reduced oxidative stress/eNOS-dependent PKGIα oxidation and polymerization resulting in a higher fraction of PKGIα monomers, which translocated back to the cytosol. Consequently, diminished NO levels, sGC activity, cGMP concentration, and PKGIα activity in HFpEF increased upon empagliflozin leading to improved phosphorylation of myofilament proteins. In skinned HFpEF cardiomyocytes, empagliflozin improved cardiomyocyte stiffness in an anti-oxidative/PKGIα-dependent manner. Monovariate linear regression analysis confirmed the correlation of oxidative stress and PKGIα polymerization with increased cardiomyocyte stiffness and diastolic dysfunction of the HFpEF patients.

CONCLUSION

Empagliflozin reduces inflammatory and oxidative stress in HFpEF and thereby improves the NO-sGC-cGMP-cascade and PKGIα activity via reduced PKGIα oxidation and polymerization leading to less pathological cardiomyocyte stiffness.

Risk of coronary artery disease associated with polymorphism of the cytochrome P450 epoxygenase CYP2J2

BACKGROUND

Cytochrome P450 (CYP) 2J2 is expressed in the vascular endothelium and metabolizes arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs). The EETs are potent endogenous vasodilators and inhibitors of vascular inflammation. However, it is not known whether genetic polymorphisms of CYP2J2 are associated with increased cardiovascular risks.

METHODS AND RESULTS

All 9 exons of the CYP2J2 gene and its proximal promoter were sequenced in 132 patients to identify potential variants. Functional consequence of a single nucleotide polymorphism (SNP) in the promoter of CYP2J2 was further evaluated by use of transcription factor-binding and reporter assays. A total of 17 polymorphisms were identified. One of the most relevant polymorphisms in terms of frequency and functional importance is located at -50 (G-50T) in the proximal promoter of CYP2J2. Screening of 289 patients with coronary artery disease and 255 control subjects revealed 77 individuals with the G-50T SNP (17.3% of coronary artery disease patients, 10.6% of control subjects; P=0.026). The association of the G-50T polymorphism remained significant after adjustment for age, gender, and conventional cardiovascular risk factors (OR, 2.23; 95% CI, 1.04 to 4.79). The G-50T mutation resulted in the loss of binding of the Sp1 transcription factor to the CYP2J2 promoter and resulted in a 48.1+/-2.4% decrease in CYP2J2 promoter activity (P<0.01). Plasma concentrations of stable EET metabolites were significantly lower in individuals with the G-50T SNP.

CONCLUSIONS

A functionally relevant polymorphism of the CYP2J2 gene is independently associated with an increased risk of coronary artery disease.

Supplementation of hypercholesterolaemic rabbits with L-arginine reduces the vascular release of superoxide anions and restores NO production

L-arginine, the precursor of endogenous nitric oxide (NO), has been shown to enhance endothelial function and to reduce intimal plaque area in cholesterol (Chol)-fed rabbits. We have studied endogenous NO production in such animals in vitro (endothelium-dependent relaxations) and in vivo (assessed by urinary NO3- excretion) before and during chronic oral administration of L-arginine and inhibitor of NO synthesis, L-NAME. Vascular superoxide anion (O2-) production of aortic rings was measured under basal conditions and following exposure to phorbol-myristate-acetate (PMA). Cholesterol feeding reduced endothelium-dependent relaxations and decreased urinary NO3- excretion. These effects were potentiated by administration of L-NAME. L-arginine partly restored endothelium-dependent relaxations and increased NO3- excretion. PMA-stimulated O2- production was increased in aortic rings from rabbits given cholesterol ( +159 +/- 28%; mean +/- S.E.M.) or cholesterol + L-NAME ( +149 +/- 37%) as compared with controls ( -22 +/- 7%). In rabbits given cholesterol + L-arginine, O2- production was decreased to control levels ( +14 +/- 17%; P < 0.05). We conclude that the systemic synthesis of NO is impaired in cholesterol-fed rabbits, as indicated by the decreased urinary excretion of NO3-. Enhanced O2- production may further contribute to the decreased biological activity of NO in hypercholesterolaemia. L-arginine restores endothelial function in hypercholesterolaemia by enhancing NO production and by protecting NO from early breakdown by O2-.

Endothelium independent relaxation of human coronary arteries by 17 beta-oestradiol in vitro

OBJECTIVE

There is accumulating evidence that oestrogen replacement therapy protects against the development of coronary atherosclerosis and myocardial infarction in postmenopausal women. The mechanism of this protective effect is uncertain. The aim of this study was to measure the effects of 17 beta-oestradiol on human epicardial coronary artery tone.

METHODS

Coronary artery rings were obtained from explanted hearts during cardiac transplantation. The rings were suspended in organ baths for isometric tension measurements. The rings were precontracted with prostaglandin F2 alpha, and were then exposed to either 17 beta-oestradiol (0.3 nM-3 microM) or solvent control (0.2% ethanol v/v). In some rings, cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate content were measured by radioimmunoassay.

RESULTS

17 beta-Oestradiol induced a significant relaxation [maximum effect: 84(SD 18)%]. The onset of the relaxant effect occurred within 5 min, and was maximal within 40 min. The relaxation in response to 3 microM 17 beta-oestradiol was of similar magnitude in rings with and without intact endothelium. The maximum relaxation induced by 3 microM 17 beta-oestradiol was greater in arteries from hearts obtained from women than in those obtained from men [-100.0(3.0)% v -77.5(17.6)%, respectively]. The exposure of rings to 3 microM 17 beta-oestradiol for 30 min resulted in a significant increase in both cyclic AMP and cyclic GMP content, by 88% and 182%, respectively.

CONCLUSIONS

17 beta-Oestradiol produced an endothelium independent relaxation of precontracted human coronary arteries in vitro, and this effect was associated with an increase in both cyclic AMP and the cyclic GMP content. This direct relaxant effect of oestrogens on coronary arteries may contribute to the beneficial effects of oestrogen replacement therapy in postmenopausal women.

Dietary L-arginine reduces the progression of atherosclerosis in cholesterol-fed rabbits: comparison with lovastatin

BACKGROUND

We investigated whether L-arginine induces regression of preexisting atheromatous lesions and reversal of endothelial dysfunction in hypercholesterolemic rabbits, whether similar effects can be obtained by cholesterol-lowering therapy with lovastatin, and which mechanism leads to these effects.

METHODS AND RESULTS

Rabbits were fed 1% cholesterol for 4 weeks and 0.5% cholesterol for an additional 12 weeks. Two groups of cholesterol-fed rabbits were treated with L-arginine (2.0% in drinking water) or lovastatin (10 mg/d) during weeks 5 through 16. Systemic nitric oxide (NO) formation was assessed as the urinary excretion rates of nitrate and cGMP in weekly intervals. Cholesterol feeding progressively reduced urinary nitrate excretion to approximately 40% of baseline (P<.05) and increased plasma concentrations of asymmetrical dimethylarginine (ADMA), an endogenous NO synthesis inhibitor. Dietary L-arginine reversed the reduction in plasma L-arginine/ADMA ratio and partly restored urinary excretion of nitrate and cGMP (each P<.05 vs cholesterol) but did not change plasma cholesterol levels. L-Arginine completely blocked the progression of carotid intimal plaques, reduced aortic intimal thickening, and preserved endothelium-dependent vasodilator function. Lovastatin treatment reduced plasma cholesterol by 32% but did not improve urinary nitrate or cGMP excretion or endothelium-dependent vasodilation. Lovastatin had a weaker inhibitory effect on carotid plaque formation and aortic intimal thickening than L-arginine. L-Arginine inhibited but lovastatin potentiated superoxide radical generation in the atherosclerotic vascular wall.

CONCLUSIONS

Dietary L-arginine improves NO-dependent vasodilator function in cholesterol-fed rabbits and completely blocks the progression of plaques via restoration of NO synthase substrate availability and reduction of vascular oxidative stress. Lovastatin treatment has a weaker inhibitory effect on the progression of atherosclerosis and no effect on vascular NO elaboration, which may be due to its stimulatory effect on vascular superoxide radical generation.

Comparison of transthoracic and transesophageal echocardiography for detection of abnormalities of prosthetic and bioprosthetic valves in the mitral and aortic positions

Two-dimensional echocardiography is the diagnostic procedure of choice for evaluation of prosthetic valve abnormalities. However, transthoracic echocardiography (TTE) may be limited owing to acoustic shadowing and poor acoustic windows. Some of these limitations may be overcome by transesophageal echocardiography (TEE). One hundred twenty-six patients with 148 prosthetic valves (113 bioprostheses and 35 mechanical devices) were studied by M-mode and 2-dimensional TTE and TEE. Prosthetic valve morphology was confirmed by surgery or autopsy in all cases; 124 prostheses were classified as diseased (33 endocarditis, 8 thrombi, and 83 degeneration defined as leaflet thickening > 3 mm with restricted motion) and 24 as normal. Prosthetic valve endocarditis and thrombi were correctly identified by TTE in 12 of 33 (36%) and 1 of 8 (13%) prostheses, respectively, but could be diagnosed by TEE in 27 of 33 (82%; p < 0.001) and 8 of 8 (100%; p < 0.01), respectively. Compared with TTE, TEE had a higher sensitivity for morphologic prosthetic valve abnormalities in patients with either bioprostheses (88 [87%] vs 66 [65%] of 101 prostheses; p < 0.01) or mechanical devices (19 [83%] vs 5 [22%] of 23 prostheses; p < 0.01) and in patients with a prosthesis in either the aortic (49 [77%] vs 32 [50%] of 64; p < 0.01) or mitral (58 [97%] vs 39 [65%] of 60; p < 0.001) position. Overall, sensitivity and specificity were 57 and 63%, respectively, for TTE, and 86 and 88%, respectively, for TEE.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of patent foramen ovale permitting paradoxic embolism

OBJECTIVES

We sought to analyze the morphologic and functional characteristics of the patent foramen ovale in patients with different clinical likelihoods for paradoxic embolism.

BACKGROUND

The incidence of patent foramen ovale is increased in patients with otherwise unexplained arterial ischemic events. Because signs of venous thrombosis are absent in most patients, the diagnosis of paradoxic embolism is often questioned, even when patent foramen ovale is the only potential explanation for the ischemic event.

METHODS

Seventy-eight patients with a patent foramen ovale detected by contrast transesophageal echocardiography were studied: 21 patients with an otherwise unexplained arterial ischemic event and clinical evidence implying paradoxic embolism (group I), 30 patients with an unexplained ischemic event but no clinical evidence for paradoxic embolism (group II) and 27 patients without an ischemic event (group III).

RESULTS

During transesophageal contrast echocardiography, patients in group I had more severe right to left shunting (mean +/- SD 52 +/- 16% of the left atrial area filled with contrast medium) and a wider opening of the patent foramen ovale (7.1 +/- 3.6-mm separation between the septum primum and the septum secundum) than did patients in group II (35 +/- 15% and 4.4 +/- 3.2 mm, respectively, p < 0.001) or group III (23 +/- 12% and 3.0 +/- 2.0 mm, respectively, p < 0.001). The incidence of atrial septal aneurysm was similar in the three groups. Severe contrast shunting (> or = 50% of the left atrial area filled with contrast medium) and wide opening of the patent foramen ovale (> or = 5-mm separation) revealed a high sensitivity (71% and 86%, respectively) and high specificity (86% and 96%, respectively) for identification of group I patients.

CONCLUSIONS

Right to left contrast shunting is more severe and opening of the patent foramen ovale is larger in patients with ischemic arterial events considered to be due to paradoxic embolism. In patients with a patent foramen ovale as the only potential cause for ischemic events and no signs of venous thrombosis, morphologic and functional variables assessed by transesophageal echocardiography may be helpful in estimating the likelihood of paradoxic embolism.

Asymmetric dimethylarginine is an independent risk factor for coronary heart disease: results from the multicenter Coronary Artery Risk Determination investigating the Influence of ADMA Concentration (CARDIAC) study

BACKGROUND

Asymmetric dimethylarginine (ADMA) plasma levels have been shown to be elevated in diseases related to endothelial dysfunction such as hypertension, hyperlipidemia, diabetes mellitus, and others. It has been shown that ADMA predicts cardiovascular mortality in patients who have coronary heart disease (CHD). However, the question whether ADMA is an independent risk factor for CHD still remains unresolved.

METHODS

The CARDIAC study is a multicenter case-control study, designed to detect differences in ADMA plasma levels between patients with CHD and controls from the general population. We included in our analysis 131 cases and 131 controls, matched for age, sex, and body mass index.

RESULTS

We found that cases had higher ADMA plasma levels than controls (0.70 micromol/L [0.59-0.87 micromol/L] vs 0.60 micromol/L [0.54-0.69 micromol/L], P < .001). To evaluate the predictive power of ADMA regarding CHD, we calculated 2 multivariate logistic regression models including laboratory parameters and traditional risk factors. The odds ratio for ADMA in the multivariate model including the laboratory characteristics was 2.59 (1.61-4.17; P < .001); the odds ratio for the multivariate model including other risk factors was 6.04 (2.56-14.25; P < .001) for the third tertile (>0.72 micromol/L) versus the first (<0.58 micromol/L).

CONCLUSIONS

We conclude from the results of our study that ADMA is an independent risk factor for CHD.

Lipophilic statins interfere with the inhibitory effects of clopidogrel on platelet function — a flow cytometry study

AIMS

Clopidogrel is a pro-drug which is converted to an active, unstable drug by cytochrome P450 (CYP). The active drug irreversibly blocks one specific platelet adenosine 5'-diphosphate (ADP) receptor (P2Y12). It has been recently suggested that the most abundant human CYP isoform, 3A4, activates clopidogrel. Since certain lipophilic statins (i.e. simvastatin, atorvastatin, lovastatin) are a substrate of CYP3A4, we were interested in potential drug interactions between clopidogrel and statins.

METHODS

In patients with coronary artery disease (n=47) in whom clopidogrel treatment was initiated for balloon angioplasty and stent implantation, blood samples were taken at 0, 5 and 48 h after oral administration of clopidogrel (loading dose 300 mg, followed by 75 mg daily). ADP-stimulated (1, 10, 100 micromol/l) expression of P-selectin (CD62P) on platelets was measured by flow cytometry, and used as a marker for the antiplatelet effect of clopidogrel.

RESULTS

Pre-treatment with statins (atorvastatin, simvastatin) reduced significantly (10 micromol/l ADP stimulation) the inhibitory effects of clopidogrel during the loading phase (relative reduction after 5 h 29.3%) and, to a lesser extent during the maintenance phase (relative reduction after 48 h 16.6%). In addition we found a considerable individual heterogeneity in the response and three patients (6%) were identified in whom clopidogrel exerted almost no effect.

CONCLUSION

Certain statins which are substrates of the CYP3A4 isoform competitively inhibit the metabolic activation of clopidogrel. As a result the relative clopidogrel induced platelet inhibition (P-selectin-expression) is diminished--but still there is a relative clopidogrel effect of more than 80% in the maintenance phase. It may be reasonable to test the therapeutic efficacy of clopidogrel in those patients who require long-term treatment.

Safety and Efficacy of Enoxaparin Compared With Unfractionated Heparin and Oral Anticoagulants for Prevention of Thromboembolic Complications in Cardioversion of Nonvalvular Atrial Fibrillation

Background— Anticoagulation in cardioversion of atrial fibrillation is currently performed with unfractionated heparin (UFH) and oral anticoagulants, with or without guidance by transesophageal echocardiography (TEE). Low-molecular-weight heparins may reduce the risk of bleeding, may obviate the need for intravenous access, and do not require frequent anticoagulation monitoring.

Methods and Results— In a randomized, prospective multicenter trial, we compared the safety and efficacy of enoxaparin administered subcutaneously with intravenous UFH followed by the oral anticoagulant phenprocoumon in 496 patients scheduled for cardioversion of atrial fibrillation of >48 hours’ and ≤1 year’s duration. Patients were stratified to cardioversion with (n=431) and without (n=65) guidance by TEE. The study aimed to demonstrate noninferiority of enoxaparin compared with UFH+phenprocoumon with regard to the incidence of embolic events, all-cause death, and major bleeding complications. Secondary end points included successful cardioversion, maintenance of sinus rhythm until study end, and minor bleeding complications. Of 496 randomized patients, 428 were analyzed per protocol. Enoxaparin was noninferior to UFH+phenprocoumon with regard to the incidence of the composite primary end point in a per-protocol analysis (7 of 216 patients versus 12 of 212 patients, respectively; P =0.016) and in an intention-to-treat analysis (7 of 248 patients versus 12 of 248 patients, respectively; P =0.013). There was no significant difference between the 2 groups in the number of patients reverted to sinus rhythm.

Conclusions— Enoxaparin is noninferior to UFH+phenprocoumon for prevention of ischemic and embolic events, bleeding complications, and death in TEE-guided cardioversion of atrial fibrillation. Its easier application and more stable anticoagulation may make it the preferred drug for initiation of anticoagulation in this setting.

Vascular release of superoxide radicals is enhanced in hypercholesterolemic rabbits

Production/release of superoxide anions from aortic rings was measured by a modified lucigenin-enhanced chemiluminescence (CL) technique. The aortic rings were obtained from control and cholesterol-fed (1% for 12 weeks) rabbits. The CL signal was significantly increased in aortic wall of cholesterol-fed rabbits. Pretreatment with oxypurinol, an inhibitor of xanthine oxidase, had a slight but insignificant effect on the CL response produced by aortic rings from control animals but significantly reduced CL response to aortic rings from cholesterol-fed rabbits. Pretreatment with diethyldithiocarbamate (DETC), an inhibitor of intrinsic superoxide dismutase (SOD), increased the CL signal for both animal groups, but this increase was greatly aggravated in aortic rings from hypercholesterolemic rabbits. Addition of phorbol 12-myristate 13 acetate (PMA) to stimulate the respiratory burst of wall-adherent and/or resident leukocytes had only slight effect on the CL response to aortic rings from control animals but extensively stimulated photon emission of aortic rings from cholesterol-fed rabbits. These findings are in agreement with the concept that the arterial wall in hypercholesterolemia and/or atherosclerosis is under increased "oxidative stress."

Alpha-adrenoceptor-mediated positive inotropic effect of phenylephrine in isolated human ventricular myocardium

In isolated human ventricular myocardium the alpha-adrenoceptor agonist phenylephrine had a positive inotropic effect in preparations from 9 of 14 patients. This effect was seen in the presence of the beta-adrenoceptor-blocking agent propranolol but was nearly abolished by the alpha-adrenoceptor blocking agent prazosin. In contrast to the beta-adrenoceptor-mediated positive inotropic effect, the effect of phenylephrine was accompanied by a prolongation of the isometric contraction. The results suggest that alpha-adrenoceptors exist in human ventricular myocardium.