Bauer Ep

Myocytes Die by Multiple Mechanisms in Failing Human Hearts

&NA; We tested the hypothesis that myocyte loss in failing human hearts occurs by different mechanisms: apoptosis, oncosis, and autophagic cell death. Explanted hearts from 19 patients with idiopathic dilated cardiomyopathy (EF≤20%) and 7 control hearts were analyzed. Myocyte apoptosis revealed by caspase‐3 activation and TUNEL staining occurred at a rate of 0.002±0.0005% (P<0.05 versus control) and oncosis assessed by complement 9 labeling at 0.06±0.001% (P<0.05). Cellular degeneration including appearance of ubiquitin containing autophagic vacuoles and nuclear disintegration was present at the ultrastructural level. Nuclear and cytosolic ubiquitin/protein accumulations occurred at 0.08±0.004% (P<0.05). The ubiquitin‐activating enzyme E1 and the ligase E3 were not different from control. In contrast, ubiquitin mRNA levels were 1.8‐fold (P<0.02) elevated, and the conjugating enzyme E2 was 2.3‐fold upregulated (P<0.005). The most important finding, however, is the 2.3‐fold downregulation of the deubiquitination enzyme isopeptidase‐T and the 1.5‐fold reduction of the ubiquitin‐fusion degradation system‐1, which in conjunction with unchanged proteasomal subunit levels and proteasomal activity results in massive storage of ubiquitin/protein complexes and in autophagic cell death. A 2‐fold decrease of cathepsin D might be an additional factor responsible for the accumulation of ubiquitin/protein conjugates. It is concluded that in human failing hearts apoptosis, oncosis, and autophagy act in parallel to varying degrees. A disturbed balance between a high rate of ubiquitination and inadequate degradation of ubiquitin/protein conjugates may contribute to autophagic cell death. Together, these different types of cell death play a significant role for myocyte disappearance and the development of contractile dysfunction in failing hearts. (Circ Res. 2003;92:715–724.)

Threshold concentrations of endothelin-1 potentiate contractions to norepinephrine and serotonin in human arteries. A new mechanism of vasospasm?

Endothelin-1 is an endothelium-derived vasoconstrictor peptide. Its circulating levels are below those known to evoke direct vascular effects. To study whether low concentrations of endothelin-1 potentiate the effects of other vasoconstrictor hormones, we suspended isolated human internal mammary and left anterior descending coronary artery rings in organ chambers for isometric tension recording. In mammary artery rings, the contractions to norepinephrine (3 x 10(-8) M) were potentiated by threshold (3 x 10(-10) M) and low concentrations (10(-9) M) of endothelin-1 (96 +/- 35% and 149 +/- 58% increase from control; p less than 0.01 and 0.001; n = 6). The inhibitor of endothelial nitric oxide formation L-NG-monomethyl arginine did not affect the potentiating effects of the peptide. The calcium antagonist darodipine (10(-7) M) prevented the potentiation of the response to norepinephrine evoked by endothelin-1. Similarly, contractions to serotonin (10(-7) or 3 x 10(-8) M) were amplified by endothelin-1 (3 x 10(-10) M) in the mammary (30 +/- 9%) and in the coronary arteries (59 +/- 25%). Endothelin-1 (10(-9) M) further potentiated the response (57 +/- 23% in mammary and 87 +/- 26% in coronary arteries; p less than 0.05; n = 7 and 3). The sensitivity of mammary arteries to calcium chloride was markedly enhanced in the presence of endothelin-1 (3 x 10(-10) M; concentration shift, eightfold; p less than 0.01; n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Structural correlate of atrial fibrillation in human patients

OBJECTIVE We tested the hypothesis that structural remodeling of cellular connections, alterations in the expression of connexins (Cx), and an increase in fibrosis represent anatomic substrates of atrial fibrillation (AF). METHODS In 31 patients with AF undergoing a Maze procedure and 22 patients in sinus rhythm (SR), biopsies were taken intraoperatively from the right atrial (RA) free wall and appendages and investigated with immunoconfocal and electron microscopy. RESULTS All patients with AF exhibited a concomitant lateralization of gap junctional proteins Cx43 and Cx40, and N-cadherin (the major mechanical junction protein), instead of being confined to the intercalated discs, as observed in SR. These results were confirmed by quantitative immunoconfocal analysis and electron microscopy. Among diverse junctional proteins, in AF, Cx40 was markedly heterogeneous in distribution. As compared with the SR group, Cx43 was significantly decreased in AF by 57% in RA appendages and by 56% in RA free wall. Cx40 was reduced by 54% in appendages, but had a tendency to be increased in the RA free wall. Collagen I was significantly higher in AF than in SR by 48% in RA appendages and by 69% in the RA free wall tissues. CONCLUSIONS The structural correlate of AF comprises extensive concomitant remodeling of mechanical and electrical junctions, reduction of Cx43, heterogeneous distribution of Cx40 in terms of different amounts of Cx40 in different RA tissues or in spatially adjacent regions of atrial myocardium. These changes, together with augmentation of fibrosis, may underlie localized conduction abnormalities and contribute to initiation and self-perpetuation of re-entry pathways and AF.

Gap junction remodeling and altered connexin43 expression in the failing human heart

Gap junctions (GJ) are important determinants of cardiac conduction and the evidence has recently emerged that altered distribution of these junctions and changes in the expression of their constituent connexins (Cx) may lead to abnormal coupling between cardiomyocytes and likely contribute to arrhythmogenesis. However, it is largely unknown whether changes in the expression and distribution of the major cardiac GJ protein, Cx43, is a general feature of diverse chronic myocardial diseases or is confined to some particular pathophysiological settings. In the present study, we therefore set out to investigate qualitatively and quantitatively the distribution and expression of Cx43 in normal human myocardium and in patients with dilated (DCM), ischemic (ICM), and inflammatory cardiomyopathies (MYO). Left ventricular tissue samples were obtained at the time of cardiac transplantation and investigated with immunoconfocal and electron microscopy. As compared with the control group, Cx43 labeling in myocytes bordering regions of healed myocardial infarction (ICM), small areas of replacement fibrosis (DCM) and myocardial inflammation (MYO) was found to be highly disrupted instead of being confined to the intercalated discs. In all groups, myocardium distant from these regions showed an apparently normal Cx43 distribution at the intercalated discs. Quantitative immunoconfocal analyis of Cx43 in the latter myocytes revealed that the Cx43 area per myocyte area or per myocyte volume is significantly decreased by respectively 30 and 55% in DCM, 23 and 48% in ICM, and by 21 and 40% in MYO as compared with normal human myocardium. In conclusion, focal disorganization of GJ distribution and down-regulation of Cx43 are typical features of myocardial remodeling that may play an important role in the development of an arrhythmogenic substrate in human cardiomyopathies.

Different activation of the endothelial L-arginine and cyclooxygenase pathway in the human internal mammary artery and saphenous vein.

The endothelium releases substances controlling vascular tone and platelet function. We investigated mediators of endothelium-dependent responses in human internal mammary arteries and saphenous veins. The inhibitor of nitric oxide formation, NG-monomethyl L-arginine, enhanced the sensitivity to norepinephrine (fivefold) and evoked more pronounced endothelium-dependent contractions in internal mammary arteries (19 +/- 6% of 100 mM KCl) than in saphenous veins (2 +/- 1%; p less than 0.005). In internal mammary arteries, NG-monomethyl L-arginine, but not indomethacin, markedly reduced endothelium-dependent relaxations to acetylcholine (from 95 +/- 2% to 39 +/- 7%; p less than 0.005) and prevented those to histamine (78 +/- 6% to 4 +/- 3%; p less than 0.005). In saphenous veins, endothelium-dependent relaxations to acetylcholine were weak (24 +/- 11%), while nitric oxide caused comparable relaxations (85 +/- 3%) as in internal mammary arteries (80 +/- 5%; NS). NG-Monomethyl L-arginine prevented the relaxations to acetylcholine and unmasked endothelium-dependent contractions (30 +/- 10%). Indomethacin and the thromboxane synthetase inhibitor CGS-13080 augmented relaxations of saphenous veins to acetylcholine from 24 +/- 11% to 46 +/- 9% (p less than 0.05). Histamine-evoked contractions were converted to endothelium-dependent relaxations by indomethacin and the thromboxane A2/endoperoxide receptor antagonist SQ-30741 (38 +/- 3% and 40 +/- 6%; p less than 0.05) but not CGS-13080. Thus, 1) nitric oxide mediates endothelium-dependent relaxations in human arteries and veins; 2) internal mammary arteries release more nitric oxide than do saphenous veins, and 3) in saphenous veins, the effects of nitric oxide are reduced by endothelium-derived contracting factors originating from the cyclooxygenase pathway.

Dealing with dilated ascending aorta during aortic valve replacement: advantages of conservative surgical approach.

Five to fifteen percent of patients undergoing aortic valve replacement (AVR) will have an ascending aortic aneurysm requiring a concomitant surgical procedure. On the other hand, a dilated ascending aorta is known to be a potential source of complications after AVR. From 1972 to 1988, 2278 AVR, either isolated or combined with a second cardiac procedure, were performed in our institution. In the same time interval, a dilated ascending aorta was treated in additional 291 consecutive patients during AVR. Three different surgical options were employed: aortic remodelling and external wall support in 164 patients (56.4%), composite graft replacement in 81 patients (27.8%) and a supracoronary graft in 46 patients (15.8%). Early mortality was 4.8%. Aortic remodelling plus external wall support had the lowest early mortality (1.8%) and the best 8-year survival (89.6%). Supracoronary grafting had a higher early mortality (6.4%) and lower 8-year survival (73.2%). The results of the composite graft were least favourable: early mortality was 9.8% and 8-year survival 76.5%. The results point out the necessity for instituting the appropriate surgical procedure for a dilated ascending aorta during AVR. They show that conservative aortic surgery with preservation of endothelial lining gives excellent early and late results.

Different interactions of platelets with arterial and venous coronary bypass vessels

We studied the interaction of platelets with the wall of human internal mammary arteries and saphenous veins, suspended in organ chambers for measurement of isometric tension. Vessels were obtained during coronary bypass surgery and cut into 5 mm rings; in some the endothelium was chemically removed. Rings from several patients were randomly chosen for each experiment, and in each ring six concentrations of platelets (from healthy blood donors; 1-75 x 10(3)/microliters) were tested consecutively and concentration-response curves constructed; the areas under these curves were used for statistical comparisons. In rings of internal mammary artery contracted in response to noradrenaline, aggregating platelets induced endothelium-dependent relaxation which was prevented by apyrase (0.67 U/ml ADPase activity) and L-NG-monomethylarginine (1 mmol/l). By contrast, in saphenous vein rings contracted in response to noradrenaline, aggregating platelets induced only a further increase in tension. In quiescent vessels, the platelet-induced contraction did not occur in arteries with endothelium but that in veins was greater and facilitated by endothelium. Preincubation of platelets with aspirin (10 mumol/l) reduced the contraction in both vessels, but contraction was abolished only in the presence of both the thromboxane receptor antagonist SQ-30741 and the serotoninergic (5HT2) receptor antagonist ketanserin. These findings show that platelet-derived ADP causes release of nitric oxide by the endothelium of internal mammary artery but not of saphenous vein; thromboxane A2 and serotonin mediate contraction in vein but not artery with endothelium. These differences may contribute to differences in graft function and the clinical efficacy of antiplatelet drugs.

Mitral annuloplasty in patients with ischemic versus dilated cardiomyopathy

OBJECTIVE Mitral regurgitation is a frequent finding in patients with end-stage cardiomyopathy predicting poor survival. Conventional treatment consists medical treatment or cardiac transplantation. However, despite severely decreased left ventricular function, mitral annuloplasty may improve survival and reduce the need for allografts. METHODS From January 1996 to July 2002, 121 patients with severe end-stage dilated (DCM) or ischemic cardiomyopathy (ICM), mitral regurgitation > or =2, and left ventricular ejection fraction < or =30% underwent mitral valve annuloplasty using a flexible posterior ring. DCM was diagnosed in 30 patients (25%), whereas ICM was found in 91 patients (75%). Concomitant tricuspid valve repair was performed in 14 (46.6%) patients in the DCM, and in 11 (12%) in the ICM group (P=0.0001), coronary artery bypass grafting in three (10%) in the DCM, and in 78 patients (86%) in the ICM group (P<0.00001). The mean follow-up time was 567+/-74 days in the DCM and 793+/-63 days in the ICM group (ns). RESULTS Early mortality was 6.6% (8/121), and was equal for both groups. Improvement in NYHA class (DCM 3.3+0.1-1.8+/-0.16; ICM from 3.2+0.04 to 1.7+/-0.07) were equal between groups after 1 year. Seventeen (15%) late deaths occurred during the follow-up period. There was no difference in the 2-year actuarial survival between groups (DCM/ICM 0.93/0.85). Risk factors for mitral reconstruction failure, defined as regurgitation > or =2 after 1 year, were preoperative NYHA IV in the DCM group (P=0.03), a preoperative posterior infarction (P=0.025), decreased left ventricular function (P=0.043), larger ring size (P=0.026) and preoperative renal failure (P=0.05) in the ICM group. Risk factors for death were larger ring size (P=0.02) and an increased LVEDD (P=0.027) in the DCM group and the postoperative use of IABP (P=0.002), renal failure (P=0.001), and a larger preoperative LVESD (P=0.035) in the ICM group. CONCLUSION Mitral reconstruction with a posterior annuloplasty using a flexible ring is effective in patients with severely depressed left ventricle function and has an acceptable operative mortality. Mid-term results are superior to medical treatment alone and comparable to cardiac transplantation.

Thrombin-induced endothelium-dependent inhibition and direct activation of platelet-vessel wall interaction. Role of prostacyclin, nitric oxide, and thromboxane A2.

BACKGROUND Platelet-vessel wall interaction plays an important role in acute cardiovascular disorders. Thrombin is a potent platelet activator but also has profound effects on the endothelium. Endothelial cells possess antithrombotic activity by releasing nitric oxide and prostacyclin, both potent vasodilators and platelet inhibitors. We studied the role of thrombin as a regulator of platelet-vessel wall interaction in isolated human arteries suspended in organ chambers for isometric tension recording. METHODS AND RESULTS In arteries with endothelium, thrombin (0.01 to 1 U/mL) induced endothelium-dependent relaxations, which were reduced by the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 10(-4) mol/L) and/or indomethacin (10(-5) mol/L). Human platelets (75,000/microL) evoked only marginal contractions in arteries with endothelium (3 +/- 3% of the contraction to KCl 100 mmol/L; NS), which were markedly enhanced by endothelial removal (22 +/- 4%; P < .05). Thrombin (1 U/mL) did not affect the response to platelets in arteries with (6 +/- 5%; NS) but induced a huge contraction in rings without endothelium (53 +/- 6%; P < .01 versus control without endothelium). The potent contraction to thrombin-activated platelets (1000 to 75,000/microL) in arteries without endothelium was markedly inhibited by the thromboxane A2 synthetase/receptor antagonist ridogrel (10(-5) mol/L; P < .005 versus control) and the single-acting thromboxane receptor blocker SQ-30741 (10(-7) mol/L; P < .01 versus control). CONCLUSIONS Thus, thrombin directly stimulates platelets to release thromboxane A2, inducing potent vasoconstriction, which is prevented by the simultaneous thrombin-induced release of prostacyclin and nitric oxide from endothelial cells. In arteries devoid of functional endothelial cells, as occurs in patients with coronary artery disease, a combined inhibition of thromboxane production and action provides a potent therapeutic tool to interfere with the thrombin-induced activation of platelet-vessel wall interaction.

Do patients want minimally invasive aortic valve replacement

OBJECTIVE Access to aortic valve can be performed through small incisions. However, a considerable advantage of this approach has not been proven by randomized studies so far. We wanted to elucidate the opinion of patients when they are informed objectively about advantages and disadvantages of minimally invasive approach prior to operation. METHODS This prospective study was performed with 27 patients undergoing isolated aortic valve replacement. These patients were informed prior to operation by the same resident concerning objective data. A photograph was shown illustrating a patient with postoperative wound after a standard- and a mini-incision, respectively. After the interview the patient could decide between full and partial sternotomy. RESULTS After the interview 21/27 (78%) patients preferred to have a full sternotomy (group F) and 6/27 (22%) patients (group P) decided to have a partial sternotomy. Comments of group F: surgeon should have best exposure (n=15); cosmetics aspects unimportant (n=14); operation time as short as possible (n=7). Group P: cosmetic aspects important (n=6). Significant differences between groups (group F vs. group P): age (years), 69.1+/-1.5 vs. 49.2+/-7.3 (P=0.024); operation time (min), 142+/-7 vs. 189+/-15 (P=0.002); CK (IU/l), 111+/-11 vs. 374+/-114 (P=0.0007); CKMB (IU/l), 17+/-2 vs. 45+/-17 (P=0.006); ICU-stay (days), 2.6+/-0.2 vs. 3.2+/-0.2 (P=0.044). Pericardial effusion requiring drainage was observed in two patients of group P. One patient of group P suffered myocardial infarction. CONCLUSION When patients are informed objectively about advantages and disadvantages of minimal invasive aortic valve surgery only a smaller number decides to have a mini incision. The patients preferring short incisions are significantly younger since cosmetic aspects are more important. Longer duration of operation may be due to longer hemostasis based on limited exposure. Air bubbles due to inadequate de-airing might be responsible for higher CK and CK-MB levels in group P.