Influence of systemic hypothermia on the myocardial oxygen tension during extracorporeal circulation: comparative study in German Landrace pigs.

During extracorporeal circulation (ECC) controlled hypothermia is a common method of myocardial protection due to a reduction of the myocardial oxygen consumption. Although the beneficial aspects of hypothermia on the myocardial metabolism have been widely demonstrated the effect of hypothermia on the myocardial oxygen tension (PmyO2) is unclear. For this reason the PmyO2 of German Landrace pigs (male, three months of age) during ECC was analysed under mild hypothermia (32°C, n = 6 pigs) and under normothermia (n = 10 pigs, control group) within a time period of 23 min (1400 sec). Flexible invasive Clark type microcatheters were used to measure the PmyO2 in the beating heart. During normothermal ECC a continuous PmyO2 increase from 36.5 ± 15.8 mmHg to 52.6 ± 27.2 mmHg (+44.1%) after 1400 sec was measured (p = 0.02). In contrast, mild hypothermia caused a continuous PmyO2 decrease from initially 46.9 ± 17.5 mmHg to 36.7 ± 20.8 mmHg (-21.8%, p < 0.013) in the test period. Electrocardiography revealed no signs of ischemia or arrhythmia during normo- and hypothermic ECC. It seems obvious that mild hypothermia results in a reduction of the oxygen transfer to the myocardial cells and that this effect outweighs the beneficial effects of hypothermia in the myocardium which are related to reduced oxygen consumption. However, in mild hypothermia oxygen supply to the myocardium remained sufficient for normal myocardial function.

Cutaneous and muscular microcirculation in patients with terminal heart failure awaiting transplantation.

Heart failure patients are clinically characterized by extreme cardiomegaly, breathlessness, fluid retention and an early onset of fatigue. Studies have shown generalized restricted blood flow in those patients. Furthermore animal experiments proved an impaired blood flow and a diminished oxygen supply of the skeletal muscle in animals with chronic heart failure. Patients with chronic heart failure are limited to the extent of their ability to regulate their arterial pressure, especially in physical activity. It is however unclear in what way restriction of blood flow in the main arteries correlates with those in capillaries and to what extent. In this study it was examined the depth of capillary circulatory restriction as well as the disregulation of oxygen partial pressure in skeletal muscle in rest and stress conditions, in patients with terminal heart failure.

Influence of polymeric microspheres on the myocardial oxygen partial pressure in the beating heart of pigs.

Injection of labeled microspheres is an established method in animal models to analyze the capillary organ blood flow at different time points. However, the microspheres can lead to stenoses of the capillary lumen, which might affect tissue oxygen supply. Our study aimed to investigate the influence of repeated injections of microspheres into the left coronary artery on the tissue oxygen partial pressure (pO(2)) in the downstream supplied myocardium of Göttingen minipigs. Tests (n=6 pigs each) were performed with two differently sized microspheres (ø=10 ± 0.1 µm (M10) or ø=15 ± 0.15 µm (M15)) from polystyrene. The pO(2) was measured in the midmyocardium of the left and right ventricle for 6 min continuously after each of five injections (1 × 10(6) microspheres each). There was a time laps of 12 min between each injection. In addition, the influence of the carrier solution was analyzed solely in the identical time frame. pO(2) decreased significantly in the myocardial area supplied by the ramus interventricularis paraconalis after injection of M15 microspheres. In contrast, the application of the M10 microspheres did not change the myocardial pO(2). This finding suggests to use microspheres with diameters not exceeding 10 µm for the coronary blood flow assessment.

Coronary surgery in dialysis-dependent patients with end-stage renal failure with and without extracorporeal circulation.

Coronary artery bypass grafting (CABG) in dialysis-dependent patients with end-stage renal failure (ESRF) has become the standard treatment for CAD in this patient group, but is still considered as a risk procedure due to the increased mortality and morbidity. The avoidance of extracorporeal circulation in dialysis-dependent patients seems to be an attractive alternative. This retrospective study analyzed and compared our experience with CABG surgery with and without extracorporeal circulation in dialysis-dependent patients with ESRF. We analyzed the clinical results of isolated CABG in 73 dialysis-dependent patients with ESRF with and without the use of extracorporeal circulation. The on-pump group consisted of 43 patients (7 female and 36 male, 65 +/- 7.3 years) and the off-pump group included 30 patients (4 female and 26 male, 67 +/- 7.2 years). Demographic and preoperative data were comparable in both groups. Overall hospital mortality rate was 4.2 % (n = 3), two patients (4.6 %) in the on-pump group and one patient (3.3 %) in the off-pump group died due to noncardiac reasons. Morbidity was comparable in both groups. The mean number of grafts was 3.1 +/- 0.9 in the on-pump group and 2.9 +/- 0.8 in the off-pump group. During follow-up, 13 patients (30.2 %) in the on-pump group died, nine of these patients (69.2 %) due to cardiac reasons; eight patients (26.7 %) in the off-pump group died, mostly due to cardiac reasons (n = 5, 62.5 %). CABG can be performed in patients with dialysis-dependent ESRF with good clinical results and low morbidity with two different surgical approaches. Midterm results are still affected by cardiac events.

Prosthetic valve endocarditis: importance of surgical treatment.

Surgical therapy of prosthetic valve endocarditis (PVE) is still associated with a high mortality of up to 80 %. Further risk analysis and characterization of clinical features are important for a further improvement of surgical results. The aim of this retrospective study was a risk analysis of clinical features of the pre-, intra-, and postoperative period. Between February 1998 and December 2004, 70 patients (52 male, 18 female, age 62 +/- 11 years) were referred to our institution for surgical therapy of PVE. This cohort included 16 patients with early PVE and 54 patients with late PVE. Preoperative, intraoperative and postoperative features were evaluated with respect to their influence on the early postoperative course and the midterm follow-up. The aortic valve was affected in 41 patients (58.6 %) and the mitral valve in 15 patients (21.4 %). Double valve infection was recorded in 14 patients (20.0 %). Staphylococci (n = 36, 51.4 %), Streptococci (n = 9, 12.9 %) and others (n = 24, 14.5 %) were identified as causative agents in blood cultures. The hospital mortality rate was 20.0 % (n = 14), during follow-up (mean follow up: 3.3 +/- 2.5 years), a further 11 patients (15.7 %) died, resulting in an overall mortality of 35.7 %. The main predictors for hospital mortality were preoperative heart failure ( P = 0.01) and Staphylococci infection ( P = 0.01). Predictors of overall mortality were Staphylococci infection ( P = 0.01), heart failure ( P = 0.02) and abscess formation ( P = 0.02). Surgical therapy of prosthetic valve endocarditis is still associated with quite a high mortality during the early and midterm follow-up. Predictors of outcome particularly include preoperative risk constellations (heart failure, Staphylococci infection).

Malplacement of a pacemaker lead--a rare cause for aortic valve endocarditis.

Infective endocarditis of native valves following pacemaker implantation is rare but can be associated with serious complications, approaching a mortality of up to 25%. Recent publications report a frequency of pacemaker related endocarditis between 0.5 and 7%. Due to anatomical reasons the tricuspid valve is mostly affected in these patients, with involvement of the left heart valves usually secondary. We report an incidence of native aortic valve endocarditis due to a misplaced pacemaker lead into the left heart.

Influence of extra corporeal circulation on myocardial oxygen tension: results of an animal model.

BACKGROUND: Experimental data have shown the potential risk of cellular damage of the myocardium during extra corporeal circulation (ECC). The influence of ECC on myocardial oxygen tension however remained unclear. Therefore, the influence of ECC on the oxygen tension in a beating heart was investigated. METHODS: In a pig animal model flexible pO2 microcatheters were positioned in the midmyocardium of the left ventricle and the skeletal muscle and tissue oxygen tension during ECC were monitored and compared with data of a control group without ECC. RESULTS: ECC and unload of the heart caused a significantly higher increase of myocardial pO2 than in a non-ECC control group. CONCLUSION: Our findings show the beneficial effect of ECC on myocardial pO2. This may support the use of ECC in coronary artery bypass grafting because the potential myocardial injury due to ECC is not related to myocardial ischemia. On the contrary, myocardial pO2 was even increased during extracorporeal circulation in this study.

Coronary reoperation with and without cardiopulmonary bypass.

Redo coronary artery bypass grafting (CABG) is still associated with increased morbidity and mortality compared to primary operation. Myocardial protection is one of the key issues in redo on pump CABG and is still a matter of debate. Off pump redo CABG seems to be an attractive alternative as native coronary blood flow remains and cross clamping of the aorta is avoided. The aim of this retrospective study was to compare the outcome of redo CABG with and without CPB. From 1/1998 to 5/2004 redo CABG was performed in 195 patients (pts): 162 male (83.1%) and 33 female (16.9%) pts, age 66 +/- 9 years. In 160 pts, CPB with isolated antegrade myocardial protection was used for redo CABG. Off pump redo CABG was performed in 35 pts (30 male (85.7%) and 5 female (14.3%), age 67 +/- 8 years). Perioperative overall mortality rate was 3.6% (n = 7) and comparable in both groups (on pump 3.8% versus off pump 2.9%; p = 0.90), as well as perioperative myocardial infarction, intraaortic balloon pump implantation rate and secondary morbidity. Complete revascularization was achieved in 139 pts (86.9%) after on pump CABG and in 17 pts (48.6%) of the off pump group (p < 0.01). The average number of grafts was significantly higher in the on pump group (2.8 +/- 0.78 versus 1.6 +/- 0.6; p = 0.04).Furthermore, 20 pts (12.5%) in the on pump group died during follow-up (50 +/- 16 months). Five pts (25.0%) died due to cardiac reasons. In the off pump group 3 pts (8.6%) died during follow-up (44 +/- 13 months), noncardiac related. Overall survival was 83.8% in the on pump group and 88.6% in the off pump group (p = 0.92). On pump redo CABG and off pump redo CABG can be safely performed with low mortality and morbidity. Off pump redo CABG might be limited due to incomplete revascularization.

The G protein-gated potassium current I(K,ACh) is constitutively active in patients with chronic atrial fibrillation.

BACKGROUND: The molecular mechanism of increased background inward rectifier current (IK1) in atrial fibrillation (AF) is not fully understood. We tested whether constitutively active acetylcholine (ACh)-activated I(K,ACh) contributes to enhanced basal conductance in chronic AF (cAF). METHODS AND RESULTS: Whole-cell and single-channel currents were measured with standard voltage-clamp techniques in atrial myocytes from patients with sinus rhythm (SR) and cAF. The selective I(K,ACh) blocker tertiapin was used for inhibition of I(K,ACh). Whole-cell basal current was larger in cAF than in SR, whereas carbachol (CCh)-activated I(K,ACh) was lower in cAF than in SR. Tertiapin (0.1 to 100 nmol/L) reduced I(K,ACh) in a concentration-dependent manner with greater potency in cAF than in SR (-logIC50: 9.1 versus 8.2; P<0.05). Basal current contained a tertiapin-sensitive component that was larger in cAF than in SR (tertiapin [10 nmol/L]-sensitive current at -100 mV: cAF, -6.7+/-1.2 pA/pF, n=16/5 [myocytes/patients] versus SR, -1.7+/-0.5 pA/pF, n=24/8), suggesting contribution of constitutively active I(K,ACh) to basal current. In single-channel recordings, constitutively active I(K,ACh) was prominent in cAF but not in SR (channel open probability: cAF, 5.4+/-0.7%, n=19/9 versus SR, 0.1+/-0.05%, n=16/9; P<0.05). Moreover, IK1 channel open probability was higher in cAF than in SR (13.4+/-0.4%, n=19/9 versus 11.4+/-0.7%, n=16/9; P<0.05) without changes in other channel characteristics. CONCLUSIONS: Our results demonstrate that larger basal inward rectifier K+ current in cAF consists of increased IK1 activity and constitutively active I(K,ACh). Blockade of I(K,ACh) may represent a new therapeutic target in AF.

Coronary surgery in dialysis-dependent patients with end stage renal failure.

The number of patients with dialysis-dependent end stage renal failure (ESRF) and coronary heart disease (CAD) has increased in recent years. Coronary artery bypass grafting (CABG) has become the standard treatment for CAD in this patient group, but is still considered as a risk procedure due to increased mortality and morbidity. In a retrospective study we analyzed our clinical results of isolated CABG in 40 dialysis-dependent patients with ESRF (5 female and 35 male, mean age 65+/-8.4 years) and the use of extracorporeal circulation. The perioperative control group comprised 51 patients (10 female and 41 male, mean age 67+/-7.3 years) with normal renal function and isolated CABG. Demographic and preoperative data were comparable in both groups. Hospital mortality was 2.5% in patients with ESRF and 0% in patients with normal renal function. Morbidity was comparable in both groups. The mean number of grafts was 3.1+/-0.9 in the dialysis group and 2.9+/-0.8 in the control group. In the follow-up of the dialysis group (34+/-23 months) 8 patients died. CABG in patients with dialysis-dependent ESRF can be performed with good clinical results and morbidity comparable to patients with normal renal function.

Lactatdehydrogenase (LDH) prior and post implantation of ATS heart valves.

Establishing guidelines towards an assessment of prostheses dysfunction using LDH as a marker is difficult as shown by [M. Suedkamp, A.J. Lercher, F. Mueller-Riemenschneider, K. LaRosee, P. Tossios, U. Mehlhorn, Hemolysis parameters of St Jude Medical hemodynamic valves in aortic position, Int. J. Cardiol (95) (2004) 89-93]. In response to their work we would like to add our data concerning ATS valves (AP) and say a word of caution in interpreting an increase of LDH values.

Microwave ablation of an ischemic sustained ventricular tachycardia during aortocoronary bypass, mitral valve and tricuspid valve surgery guided by a three-dimensional non-fluoroscopic mapping system (CARTO).

Postinfarct patients with malignant ventricular tachyarrhythmias (VTs) are prone to an increased risk for sudden cardiac death and implantation of an internal cardioverter-defibrillator (ICD) often is recommended. In cases where the VTs are incessant or refractory to medical treatment, disruption of the macro-reentry circuit, which represents the arrhythmogenic substrate for postinfarct VTs, is a major therapeutical goal for electro-physiologists. The precise identification of this underlying macro-reentrant circuit depends on conventional mapping techniques (i.e. diastolic potentials, entrainment) and more recently by a three-dimensional non-fluoroscopic electro-anatomical mapping system (CARTO), which integrates anatomical and electrophysiological information to reconstruct a three-dimensional activation and propagation map of the relevant VT. This reports describes on a patient with recurrent, drug-refractory, hemodynamically stable monomorphic VTs on the basis of a 2-vessel coronary artery disease, reduced left ventricular ejection fraction, who was scheduled for coronary artery bypass graft operation combined with mitral valve replacement and reconstruction of the tricuspid valve. Preoperatively, the underlying mechanism of the VT was identified by CARTO mapping with a slow conduction zone and a wide exit site at the inferoapico-basal portion of the left ventricle. In close cooperation between the cardiologists and the surgeons the decision for a simultaneous ablation approach during the subsequent operation was made. Successful ablation of the VT using microwave energy was confirmed by non-inducibility of the VT in the perioperative electrophysiologic study. This case report highlights the use of CARTO mapping to identify postinfarct VTs as well as the application of microwave energy as a useful tool to cure postinfarct ventricular arrhythmias.

L-type Ca2+ current downregulation in chronic human atrial fibrillation is associated with increased activity of protein phosphatases.

BACKGROUND: Although downregulation of L-type Ca2+ current (I(Ca,L)) in chronic atrial fibrillation (AF) is an important determinant of electrical remodeling, the molecular mechanisms are not fully understood. Here, we tested whether reduced I(Ca,L) in AF is associated with alterations in phosphorylation-dependent channel regulation. METHODS AND RESULTS: We used whole-cell voltage-clamp technique and biochemical assays to study regulation and expression of I(Ca,L) in myocytes and atrial tissue from 148 patients with sinus rhythm (SR) and chronic AF. Basal I(Ca,L) at +10 mV was smaller in AF than in SR (-3.8+/-0.3 pA/pF, n=138/37 [myocytes/patients] and -7.6+/-0.4 pA/pF, n=276/86, respectively; P<0.001), though protein levels of the pore-forming alpha1c and regulatory beta2a channel subunits were not different. In both groups, norepinephrine (0.01 to 10 micromol/L) increased I(Ca,L) with a similar maximum effect and comparable potency. Selective blockers of kinases revealed that basal I(Ca,L) was enhanced by Ca2+/calmodulin-dependent protein kinase II in SR but not in AF. Norepinephrine-activated I(Ca,L) was larger with protein kinase C block in SR only, suggesting decreased channel phosphorylation in AF. The type 1 and type 2A phosphatase inhibitor okadaic acid increased basal I(Ca,L) more effectively in AF than in SR, which was compatible with increased type 2A phosphatase but not type 1 phosphatase protein expression and higher phosphatase activity in AF. CONCLUSIONS: In AF, increased protein phosphatase activity contributes to impaired basal I(Ca,L). We propose that protein phosphatases may be potential therapeutic targets for AF treatment.

[Surgical therapy of traumatic cardiologic intervention]. / Chirurgische Therapie nach traumatischen interventionellen Koronarläsionen.

Coronary perforation and entrapment of catheter materials are rare, but life-threatening complications, which often require emergency cardiosurgical treatment. Surgical options include tamponade drainage, coronary artery bypass grafting, perforation suturing, and removal of catheter materials. Surgical strategies are not standardized but mainly depend on the surgical anatomy. This is in particular true for the removal of the catheter remnants (stent, guidewire). Keeping this in mind, these patients can be treated with good clinical results.

Autoantibodies against the beta1 adrenoceptor from patients with dilated cardiomyopathy prolong action potential duration and enhance contractility in isolated cardiomyocytes.

Autoantibodies against the beta1-adrenoceptor (beta1-AAB) from patients with dilated cardiomyopathy (DCM) increase the beating frequency of cultured neonatal rat cardiomyocytes. This effect is accompanied by only a small increase in cAMP production. Here we have investigated whether beta1-AAB affect electrophysiological properties and cell shortening of isolated cardiomyocytes by interacting with the beta1-adrenoceptor. Beta1-AAB were obtained during immunoadsorption of patients with DCM and were used for experiments in isolated myocytes cultured from neonatal rat hearts, or freshly isolated from adult rat ventricles or from human right atria. The unselective beta -adrenoceptor agonist (-)-isoprenaline was studied for comparison. Immunoglobulin G (IgG) antibodies increased the spontaneous beating frequency of neonatal rat cardiomyocytes to a lesser degree than (-)-isoprenaline, but both effects were maximum and stable after 2 min. In rat ventricular and human atrial myocytes, IgG increased action potential duration (APD) in a concentration-dependent manner with larger effects on late than on early repolarization phases. Similar effects were obtained with purified beta1-AAB, whereas flow through of the chromatography column was ineffective. (-)-isoprenaline prolonged APD to the same extent during plateau and late phase of repolarization. beta1-AAB increased L-Type Ca2+ current in correspondence with the prolongation of APD. The effects of beta1-AAB and (-)-isoprenaline on APD were strongly attenuated after preincubation of the myocytes with the selective beta1-adrenoceptor antagonist (-)-bisoprolol. In addition, beta1-AAB increased cell shortening in ventricular myocytes from adult rat hearts. Beta1-AAB enhancing the beating frequency of cultured cardiomyocytes, increase L-Type Ca2+ current, APD and contractility in freshly isolated cardiomyocytes mediated via beta1-adrenoceptors. These effects may contribute to beta1-adrenoceptor-mediated cardiotoxicity in heart failure.

Early experience with a quadrileaflet stentless mitral valve.

BACKGROUND: Presently no ideal prosthesis for mitral valve replacement exists. The quadrileaflet mitral valve (SJM-Quattro-MV; St. Jude Medical, Inc, St. Paul, MN) is a chordally supported stentless bioprosthesis. Due to its specific geometry it seems to be particularly suited for mitral valve replacement. METHODS: From March 1999 to October 2000, 12 patients (ages 71+/-2 years) received the SJM-Quattro-MV. Six patients suffered from valvular stenosis and 6 patients from incompetence. Preoperatively, all patients were in New York Heart Association functional class III, with left ventricular ejection fraction amounts of 54%+/-17%. RESULTS: Eleven patients received a medium size SJM-Quattro-MV and one patient received a large size SJM-Quattro-MV. Cross-clamp time was 99.8+/-4.9 minutes. Additional procedures were coronary artery bypass grafting (n = 3) and left atrial microwave ablation (n = 2). Postoperative mortality (n = 1) was procedure related. At follow-up of 11.6+/-5.4 months, all patients were well, the transvalvular pressure gradient was 5.0+/-1.4 mm Hg, and the effective orifice area 2.7+/-0.2 cm2. CONCLUSIONS: Our preliminary experiences with the SJM-Quattro-MV presented good clinical results and promoted an optimistic way of thinking about the further development of these valve prostheses.