[Thin-walled apical ventricular aneurysm associated with hypertrophic obstructive cardiomyopathy]

HISTORY AND ADMISSION FINDINGS

A 73-year-old patient presented for routine follow-up examination for pre-diagnosed hypertrophic obstructive cardiomyopathy (HOCM). The patient's history included arterial hypertension and dyspnea on exertion.

INTERVENTIONS

Echocardiography revealed a large apical aneurysm, which had vastly increased in size over the past six months. Further evaluation by cardiac magnetic resonance (NMR) imaging confirmed the aneurysm and demonstrated a wall thickness of no more than 2 mm.

TREATMENT AND COURSE

Due to the rapid increase in size in addition to the extremely thin wall diameter the risk of spontaneous rupture was considered high and the patient was referred to surgical therapy. Echocardiographic and NMR-findings were confirmed intraoperatively. The aneurysm was resected and the postoperative progress was uneventful.

CONCLUSION

Aneurysms of the apical left ventricle can result from an underlying HOCM. In case of rapid increase of the aneurysm, aneurysmectomy should be performed.

Effects of chronic atrial fibrillation on gap junction distribution in human and rat atria

OBJECTIVES

To elucidate the structural basis for the electrophysiologic remodeling induced by chronic atrial fibrillation (AF), we investigated connexin40 and connexin43 (Cx40 and Cx43) expression and distribution in atria of patients with and without chronic AF and in an animal model of AF with additional electrophysiologic investigation of anisotropy (ratio of longitudinal and transverse velocities).

BACKGROUND

Atrial fibrillation is a common arrhythmia that has a tendency to become persistent. Since gap junctions provide the syncytial properties of the atrium, changes in expression and distribution of intercellular connections may accompany the chronification of AF.

METHODS

Atrial tissues isolated from 12 patients in normal sinus rhythm at the time of cardiac surgery and from 12 patients with chronic AF were processed for immunohistology and immunoblotting for the detection of the gap junction proteins. The functional study of the cardiac tissue anisotropy was performed in rat atria in which AF was induced by 24 h of rapid pacing (10 Hz).

RESULTS

Immunoblotting revealed that AF did not induce any significant change in Cx43 content in human atria. In contrast, a 2.7-fold increase in expression of Cx40 was observed in AF. Immunohistologic analysis indicated that AF resulted in an increase in the immunostaining of both connexins at the lateral membrane of human atrial cells. A similar spatial redistribution of the Cx43 signal was seen in isolated rat atria with experimentally-induced AF. In addition, AF in rat atria resulted in decreased anisotropy with slightly enhanced transverse conduction velocity.

CONCLUSIONS

This experimental study showed that AF is accompanied by spatial remodeling of gap junctions that might induce changes in the biophysical properties of the tissue.

Simultaneous carotid and coronary artery surgery: indications and perioperative outcome

BACKGROUND

A significant number of patients with coronary artery disease is diagnosed with additional carotid artery disease. This subset of patients has been identified as a high-risk group for cardiac and cerebral complications following surgical intervention.

METHODS

In a retrospective analysis we investigated the perioperative outcome of combined single-stage carotid endarterectomy (CEA) and coronary artery bypass grafting (CABG) in 63 patients operated between January 1989 and August 1998. In all of these patients, CEA was performed prior to CABG and before initiation of cardiopulmonary bypass.

RESULTS

Perioperative mortality rate was 7.9% (5/63) for simultaneous CEA and CABG and was due to cardiac complications in all patients. Postoperative unilateral neurological symptoms were diagnosed in 1 patient (1.7%) and were completely reversible. No neurologic events suggestive for permanent cerebral damage were observed during the 30 d postoperative period.

CONCLUSIONS

In our study combined single-stage CEA and CABG was associated with low cerebral morbidity and patient outcome was mainly determined by cardiac complications. In this subset of patients, simultaneous CEA and CABG appears to be a safe method.

Effects of modification of the allocation system on ischemia duration and costs of heart transplantation. Transplantation Cooperation UNI-NRW

BACKGROUND

In order to optimize regional utilization of transplantable thoracic organs, the seven university hospitals in North-Rhine-Westfalia have formed a transplant cooperation meanwhile approved by Eurotransplant.

METHODS

Heart transplant and organ donation activities of the cooperating hospitals in the year before the foundation of the cooperation (period A, 7/95 - 6/96) and in the year thereafter (period B, 7/96 - 6/97) were retrospectively analysed.

RESULTS

In period A, a total of 39 heart transplants and 74 heart donations were performed, whereas in period B 67 heart transplantations and 78 heart donations could be achieved. The regional utilization of the donor organs increased from 4% to 30% with a significantly shorter ischemia time of regionally or locally allocated donor hearts than of nationally or internationally allocated ones.

CONCLUSIONS

A high rate of regional or local heart transplant procedures with short ischemia times clearly demonstrate the benefits of a regionalization of heart transplant medicine for medical as well as economical reasons.

Acute effects of nitric oxide and cyclic GMP on human myocardial contractility

Evidence that the activity of nitric oxide synthase and the generation of nitric oxide (NO) within the myocardium are enhanced in several cardiovascular disorders is increasing. Findings whether NO exerts a direct effect on cardiac contractility are contradictory. Therefore, the direct effect of the NO donor sodium nitroprusside (SNP) on isometric force of contraction of human atrial and ventricular myocardium was investigated, and the question was addressed whether the effects of NO on cardiac contractility are mediated via cGMP. Experiments were performed on isolated electrically driven (1 Hz, 37 degrees C) human right atrial trabecula and left ventricular papillary muscle preparations from nonfailing and terminally failing hearts. SNP led to a concentration-dependent decrease of force of contraction (FOC) with a maximum effect at 100 micromol/l. In atrial trabecula, SNP (100 micromol/l) caused an acute decrease in basal FOC as well as in FOC after application of isoprenaline or IBMX by 12.5 +/- 5% (P < .05), 16.6 +/- 3.7% (P < .05) and 18.3 +/- 4.2% (P < .05), respectively. The negative inotropic effects could be attenuated by the guanylyl cyclase inhibitor methylene blue. In papillary muscle preparations, NO release caused a maximum decrease in basal and in isoprenaline-enhanced FOC of 11.0 +/- 1.9% (P < .05) and 23.6 +/- 1.5% (P < .05), respectively. In the presence of isoprenaline, the reduction of FOC was less pronounced in failing than in nonfailing papillary muscles. 8-bromo-cGMP caused a 38.2 +/- 5.2% decrease in atrial trabecula contractility. Both SNP and 8-bromo-cGMP caused a shortening of the contractile twitch with a premature onset of relaxation. As determined by radioimmunoassay, exposure of atrial trabecula to SNP (100 micromol) led to a 6-fold increase in myocardial cGMP concentrations, which could be attenuated by methylene blue. In conclusion, NO exerts a negative inotropic effect on human atrial and ventricular myocardium which seems to be mediated via generation of cGMP. The release of NO within the myocardium in a variety of cardiovascular disorders might explain decreases in cardiac contractility. The control of NO release could be an important target for future therapeutical interventions in these pathological conditions.

Evidence for functional relevance of an enhanced expression of the Na(+)-Ca2+ exchanger in failing human myocardium

BACKGROUND

The present study aimed at investigating the expression of the Na(+)-Ca2+ exchanger and its functional role in human failing myocardium.

METHODS AND RESULTS

Na(+)-Ca2+ exchanger mRNA and protein levels were examined in nonfailing (NF, n = 8) and failing human myocardium (New York Heart Association functional class IV) with idiopathic dilated cardiomyopathy (DCM, n = 8) or ischemic heart disease (ICM, n = 6). The inotropic effect of the Na+ channel activator BDF 9148 was determined in electrically driven left ventricular papillary muscle strip preparations (1 Hz, 37 degrees C) from nonfailing (n = 8) and failing (n = 8) human hearts. Na(+)-Ca2+ exchanger mRNA levels were significantly increased, by 79% (P < .001) in DCM and by 58% (P < .01) in ICM compared with NF; protein levels increased by 36% (P < .001) and by 20% (P < .05), respectively. BDF 9148 increased the force of contraction concentration dependently, with a similar maximal effect in NYHA class IV and NF, but was more potent in NYHA class IV as demonstrated by a significantly smaller (P < .01) EC50 value (NYHA class IV, 0.18 [0.16 to 0.22] mumol/L; NF, 1.65 [1.3 to 3.0] mumol/L). In NYHA class IV, BDF 9148 (0.1 mumol/L) restored the positive force-frequency relationship and reduced the frequency-dependent increase in diastolic tension in relation to force of contraction.

CONCLUSIONS

The increased expression of the Na(+)-Ca2+ exchanger is a possible explanation for the increased inotropic potency of the Na+ channel activator BDF 9148 in failing human myocardium. The increase in exchanger molecules could be of functional relevance for the modulation of cardiac contractility by agents that increase the intracellular Na+ concentration. Enhancement of Na(+)-Ca2+ exchanger activity might be a powerful mechanism for increasing cardiac contractility in chronic heart failure.

Sarcoplasmic reticulum Ca2+ATPase and phospholamban mRNA and protein levels in end-stage heart failure due to ischemic or dilated cardiomyopathy

Abnormalities in intracellular Ca2+ handling play a crucial role in the pathogenesis of heart failure. The reduced capacity of failing human myocardium to restore low resting Ca2+ levels during diastole has been explained by the impairment of Ca2+ uptake into the sarcoplasmic reticulum (SR) via the SR Ca2+ATPase. It is unclear whether Ca2+ATPase function, protein levels, and mRNA steady-state levels correspond to one other, and whether the cause of heart failure, namely idiopathic dilated or ischemic cardiomyopathy, produces different changes. The present study examined SR Ca2+ATPase activity and both mRNA and protein levels of SR Ca2+ATPase, phospholamban, and Gi alpha 2 in left ventricular myocardium from eight nonfailing hearts, from eight hearts of patients with idiopathic dilated cardiomyopathy (DCM), and from six hearts from patients with ischemic cardiomyopathy (ICM). Compared to nonfailing myocardium, the activity of the SR Ca2+ATPase was significantly reduced in failing myocardium from patients with DCM (36%, P < 0.01) and from patients with ICM (37%, P < 0.001). Significantly lower levels of SR Ca2+ATPase mRNA levels (55% and -56%, P < 0.001 for DCM and ICM, respectively) and phospholamban mRNA (45%, P < 0.001 for DCM; 31%, P < 0.05 for ICM) were observed in failing than in nonfailing myocardium. In contrast, no significant changes were observed at the level of proteins, Gi alpha 2 mRNA and protein levels were both significantly increased in failing myocardium. There were no differences between idiopathic dilated and ischemic cardiomyopathy concerning the examined parameter. It is concluded that reduced SR Ca2+ATPase activity contributes to an altered intracellular Ca2+ handling by the SR in both dilated and ischemic cardiomyopathic hearts. However, changes in SR Ca2+ATPase and phospholamban steady-state protein levels do not contribute to these alterations. The dissociation between protein and mRNA levels provides evidence for a posttranscriptional or post-translational regulation of these proteins. The observed alterations are not dependent on the underlying cause of end-stage heart failure.

Effects of angiotensin II and angiotensin-converting enzyme inhibitors on human myocardium

Human myocardial angiotensin II receptors and the angiotensin AT1 and AT2 receptor subtypes were characterised using the partial angiotensin II receptor agonist [125I][Sar1,IIe8]angiotensin II and the selective antagonists losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[2'((1H-tetrazol-5-yl)biphen yl-4-yl)- methyl]imidazole) and PD 123177 (1-[(4-amino-3-methylphenyl)methyl]-5-(diphenyl-acetyl)- 4,5,6,7-tetrahydro-1H-imidazol[4,5-c]pyridine-6-carboxylic acid). The density of angiotensin II receptors was higher in atrial than in ventricular myocardium. Angiotensin AT2 receptors were predominant in atria and ventricles (80-85% of total angiotensin II receptors). Only in isolated, electrically driven atrial trabeculae but not in ventricular preparations, angiotensin II did produce a concentration-dependent positive inotropic effect, which was antagonized exclusively by the angiotensin AT1 receptor antagonist losartan and which amounted to about 20% of the positive inotropic effect of milrinone and isoprenaline. The application of the angiotensin-converting enzyme inhibitors captopril, enalaprilat and ramiprilat had no inotropic effect in either tissue. It is concluded that angiotensin AT1 receptors exclusively mediate direct positive inotropic effects in atrial myocardium. Since angiotensin-converting enzyme inhibitors do not produce any inotropic effect, tonic regulation of basal force of contraction by angiotensin II does not occur.

Megakaryocytes and fibroblasts--interactions as determined in normal human bone marrow specimens

An in vitro study was performed to investigate possible interactions between megakaryocytes and bone marrow fibroblasts, both obtained from healthy donors. We were able to demonstrate that the proliferation of fibroblasts increased significantly by co-culturing these cells with megakaryocytes for 6 days. Addition of neutralizing antibodies for PDGF and TGF beta 1, caused a significant reduction of fibroblast growth. Inhibition of cell to cell contacts via tissue culture inserts generated a conspicuous impairment of fibroblast proliferation compared with megakaryocyte-fibroblast co-cultures, where contact was allowed. Hence, our findings suggest that a close spatial relationship between megakaryocytes and fibroblasts is needed for the activation of growth in normal human bone marrow. Neighbouring of megakaryocytes and fibroblasts seems to be necessary in order to achieve a certain threshold of local growth factor concentration. Our results are in keeping with the assumption that PDGF and TGF beta 1, are secreted by normal human megakaryocytes in very low concentrations and promote significantly fibroblast proliferation.

Evidence against a role of nitric oxide in the indirect negative inotropic-effect of M-cholinoceptor stimulation in human ventricular myocardium

Nitric oxide (NO) has been reported to mediate several effects in response to muscarinic cholinergic stimulation in cardiovascular tissues. Recently, an attenuation of guinea pig cardiac myocyte contraction by NO has been described. The aim of the present study was to determine whether the indirect negative inotropic effect of M-cholinoceptor stimulation in human myocardium is in part due to an effect of endogenous NO. Therefore, the effect of carbachol was studied under control conditions and during inhibition of NO-synthase by pretreatment with NG-monomethyl-L-arginine (NMMA). Functional experiments were performed in isolated, electrically driven (1 Hz, 37 degrees C) left ventricular papillary muscle strips of human myocardium. Since cytokines have been reported to be increased in the serum of patients with heart failure and could induce NO-synthase activity in failing myocardium, we compared samples from nonfailing and terminally failing (classified as NYHA IV) hearts. The indirect negative inotropic effect of carbachol (10 mumol/l) was studied in the presence of the beta-adrenoceptor agonist isoprenaline (0.03 mumol/l). After stimulation with isoprenaline, carbachol significantly (P < 0.05) reduced force of contraction. This effect was diminished in failing myocardium compared to nonfailing, probably due to the diminished inotropic response most likely due to the lower cAMP levels in response to beta-adrenoceptor stimulation in the former condition. Pretreatment with NMMA (100 mumol/l) altered the antiadrenergic effect of carbachol neither in nonfailing nor in failing preparations. Furthermore, inhibition of guanylyl cyclase, the target enzyme of NO, by preincubation with methylene blue (10 mumol/l) for 30 min had no effect on the carbachol-induced decrease in force of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)