Wolf-Peter Klövekorn

Progression From Compensated Hypertrophy to Failure in the Pressure-Overloaded Human Heart Structural Deterioration and Compensatory Mechanisms

Background—The progression of compensated hypertrophy to heart failure (HF) is still debated. We investigated patients with isolated valvular aortic stenosis and differing degrees of left ventricular (LV) systolic dysfunction to test the hypothesis that structural remodeling, as well as cell death, contributes to the transition to HF. Methods and Results—Structural alterations were studied in LV myectomies from 3 groups of patients (group 1: ejection fraction [EF] >50%, n=12; group 2: EF 30% to 50%, n=12; group 3: EF <30%, n=10) undergoing aortic valve replacement. Control patients were patients with mitral valve stenosis but normal LV (n=6). Myocyte hypertrophy was accompanied by increased nuclear DNA and Sc-35 (splicing factor) content. ACE and TGF-&bgr;1 were upregulated correlating with fibrosis, which increased 2.3-, 2.2-, and 3.2-fold over control in the 3 groups. Myocyte degeneration increased 10, 22, and 32 times over control. A significant correlation exists between EF and myocyte degeneration or fibrosis. Ubiquitin-related autophagic cell death was 0.5‰ in control and group 1, 1.05 in group 2, and 6.05‰ in group 3. Death by oncosis was 0‰ in control, 3‰ in group 1, and increased to 5‰ (groups 2 and 3). Apoptosis was not detectable in control and group 3, but it was present at 0.02‰ in group 1 and 0.01‰ in group 2. Cardiomyocyte mitosis was never observed. Conclusions—These structure-function correlations confirm the hypothesis that transition to HF occurs by fibrosis and myocyte degeneration partially compensated by hypertrophy involving DNA synthesis and transcription. Cell loss, mainly by autophagy and oncosis, contributes significantly to the progression of LV systolic dysfunction.

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.)

Hibernating Myocardium An Incomplete Adaptation to Ischemia

BACKGROUND We tested the hypothesis that hibernating myocardium represents an incomplete adaptation to a reduced myocardial oxygen supply. METHODS AND RESULTS In 38 patients, areas of hibernating myocardium were identified by angiography, multigated radionuclide ventriculography, thallium scintigraphy with reinjection, and low-dose dobutamine echocardiography. Biopsies removed at cardiac surgery showed structural degeneration characterized by a reduced protein and mRNA expression and disorganization of the contractile and cytoskeletal proteins myosin, actin, desmin, titin, alpha-actinin, and vinculin by electron microscopy, immunohistochemistry, and in situ hybridization. Additionally, an increased amount of extracellular matrix proteins resulting in a significant degree of reparative fibrosis was present. Dedifferentiation, ie, expression of fetal proteins, was absent. Apoptosis indicating suicidal cell death was found by the terminal deoxynucleotidyl transferase end-labeling method and electron microscopy. Radionuclide ventriculography showed improvement of regional function at 3 months postoperatively compared with preoperative values (mean values, 23.5% and 48%, respectively), and the echocardiographic wall-motion score index decreased from 3.4 to 1.8. The degree of severity of the morphological changes (three stages) correlated well with the extent of postoperative functional recovery: more advanced clinical improvement was observed in patients with slight and moderate morphological degeneration (stages 1 and 2), but recovery was only partial in severe degeneration (stage 3). CONCLUSIONS Cellular degeneration rather than adaptation is present in hibernating myocardium. The consequence is progressive diminution of the chance for complete structural and functional recovery after restoration of blood flow. The practical consequence from this study should be early revascularization in patients showing areas of hibernating myocardium.

Increased Expression of Cytoskeletal, Linkage, and Extracellular Proteins in Failing Human Myocardium

Experimental studies have shown that in hypertrophy and heart failure, accumulation of microtubules occurs that impedes sarcomere motion and contributes to decreased ventricular compliance. We tested the hypothesis that these changes are present in the failing human heart and that an entire complex of structural components, including cytoskeletal, linkage, and extracellular proteins, are involved in causing functional deterioration. In explanted human hearts failing because of dilated cardiomyopathy (ejection fraction </=20%), expression of alpha- and beta-tubulin, desmin, vinculin, fibronectin, and vimentin was determined by Northern and Western blot analysis and compared with normal myocardium from explants not used for transplantation. The mRNA for alpha- and beta-tubulin was increased to 2.4-fold (P<0.01) and 1.25-fold (NS), respectively; for desmin, 1.2-fold (P<0.05); for fibronectin, 5-fold (P<0.001); and for vimentin, 1.7-fold (P<0.05). Protein levels for alpha-tubulin increased 2.6-fold (P<0.02); for beta-tubulin, 1.2-fold (P<0.005); for desmin, 2.1-fold (P<0.001); for vinculin, 1.2-fold (P<0.005); for fibronectin, 2.9-fold (P<0.001); and for vimentin, 1.5-fold (P<0. 005). Confocal microscopy showed augmentation and disorganization of all proteins studied. In combination with the loss of myofilaments and sarcomeric skeleton previously reported, these changes suggest cardiomyocyte remodeling. Increased fibronectin and elevated interstitial cellularity (vimentin labeling) indicate progressive fibrosis. The present results suggest a causative role of cytoskeletal abnormalities and myofilament loss for intrinsic contractile and diastolic dysfunction in failing hearts.

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.

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.

A self-perpetuating vicious cycle of tissue damage in human hibernating myocardium.

Recently, we proposed the hypothesis that a vicious cycle exists in human hibernating myocardium (HM) between the progression of myocyte degeneration and the development of fibrosis [1]. We now investigated the pathomechanism of this cycle in more detail and established a correlation between the severity of the morphological changes and the degree of postoperative functional recovery of HM.HM was diagnosed by dobutamine echocardiography, thallium-201 scintigraphy and radionuclide ventriculography. Functional recovery was present at 3 months after coronary bypass surgery but remained unchanged at 15 months. Forty patients were subdivided into 2 groups: A with complete and B with incomplete recovery. Biopsies taken during surgery and studied by electron microscopy, immunocytochemistry, rt-PCR, and morphometry revealed myocyte degeneration and inflammatory and fibrinogenic changes in a widened interstitial space. We report here for the first time an upregulation of TGF-β1 evident by a 5-fold increase of fibroblasts and macrophages exhibiting a TGF-β1 content 3-fold larger than in control, and a > 3-fold increase in TGF-β1 mRNA by rt-PCR. The number of angiotensin converting enzyme (ACE) containing structures was increased (n/mm2: control - 11.4, A - 17.6, B - 19.2, control vs. A and B, p < 0.05). Fibrosis was more severe in group B than A or control (%: C - 10.1; A - 21.2; B - 40.6; p < 0.05). Capillary density was significantly reduced (n/mm2: C - 1152; A - 782; B - 579, p < 0.05) and intercapillary distance was widened (μm: C - 29.5, A - 36.1, B - 43.3, p < 0.05). The number of CD 3 (n/mm2: C - 5.0; A - 9.6; B - 9.4, ns) and CD 68 positive cells (n/mm2: C - 37.2; A - 80.7; B - 55.0, C vs. A p < 0.05) was elevated in HM as compared to control indicating an inflammatory reaction. Cut-off points for functional recovery are fibrosis > 32%, capillary density < 660/mm2 and intercapillary distance > 39.0 μm.In HM a self-perpetuating vicious cycle of tissue alterations leads to progressive replacement fibrosis and continuous intracellular degeneration which should be interrupted by early revascularization.

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.

Midterm results after the Mini-Maze procedure.

OBJECTIVE Atrial fibrillation (AF) is the most common arrhythmia. However, its precise electrophysiologic mechanism is still not well understood. Chronic symptomatic AF resistant to medical therapy, can successfully be treated by the Maze III procedure (M III). However, there are several publications dealing with alternative surgical techniques. This study describes technique and midterm results of a Mini-variant of the M III procedure. METHODS During a 38-month period we performed either an M III (seven patients) (group I) or a MINI-operation (45 patients) (group II) with chronic symptomatic AF and additional cardiac pathology. Patients were controlled 3.6 +/- 0.9 and 14.9 +/- 2.2 months after operation by means of thorough electrophysiological assessment, right heart catheterization, magnetic resonance imaging (MRI), echocardiography, stress-EGG and 24-h-ECG. RESULTS There was no significant differences between the two groups with regard to sex, age and duration of AF. Echocardiographic left atrial diameter (LAD) was 75 +/- 11 mm in group I and 67 +/- 8 mm in group II (P = 0.01). Whereas right atrial diameter was 62 +/- 8 mm in group I and 56 +/- 7 mm in group II (NS). Perioperative data (n = 52): aortic cross clamp time was 127 +/- 40 mm in group I and 87 +/- 21 mm in group II, (P = 0.0002). Cardiopulmonary bypass time was 185 +/- 71 mm in group I and 137 +/- 46 mm in group II, (P = 0.02). Postoperative data: there was no difference between the two groups with regard to sinus rhythm, prolonged sinus node recovery time, pacemaker (PM) in AAI-mode, inducible atrial fibrillation, reduction of left and right atrial size after a follow-up interval of 3.6 months and 1 year, respectively. CONCLUSION Midterm results are identical after M III and MINI. MINI is less complex compared to the M III procedure and there is a significant reduction of crossclamp- and ECC-time. We recommend the MINI especially for polymorbid patients, and for those with poor left ventricular function.

Cardioscopy: potential applications and benefit in cardiac surgery

OBJECTIVE Cardioscopy in open heart surgery is still not routine in most units. However, since our first report in 1996 we use this device more frequently, because we think that safety and accuracy of different surgical procedures is increased. METHODS Between 1/96 and 12/97 we performed cardioscopy in 100 patients. Indications (IND) for cardioscopy were as follows: IND (1) resection of hypertrophied septum (N = 15); IND (2) evaluation of aortic valve with low grade stenosis or insufficiency (N = 12); IND (3) removal of intracardiac foreign bodies/tumors (N = 13); IND (4) inspection of VSD prior and after repair (N = 8); IND (5) identification of paravalvular leakage (N = 8); IND (6) diagnostic purposes (N = 4); IND (7) education of surgeons and operating room staff (N = 40). During cardioplegic arrest the 5 mm rigid or flexible cardioscope (Storz, Tuttlingen, Germany) was inserted through ascending aorta, aortic valve or tricuspid valve depending on indication. RESULTS No complication occurred during cardioscopy. IND (1): there was an excellent view of all intracardiac structures. Thorough resection of hypertrophied septum was possible and there was no injury of adjacent structures or aortic valve. IND (2): all valves were inspected through a 1 cm aortic incision and the pathology of the valves was documented. In case of severe calcification, the valve was replaced although transvalvular gradient was less than 50 mm Hg. IND (3): intraventricular foreign bodies, such as felt pledges (N = 2), debris (N = 5), thrombi (N = 4) and tumors (N = 2) were entirely removed through the aortic valve with a special forceps. IND (4): anatomy of VSD was documented in all cases. It was possible to test accuracy of all patch-sutures. IND (5): all paravalvular leakages were identified even though there was heavy immobility of the mechanical valve. IND (6): a papillary muscle (N = 2) and a thrombus formation (N = 2) were diagnosed. IND (7): the surgeons and operating room staff could follow the entire procedure in all cases. CONCLUSIONS Cardioscopy is a supporting technique to clearly identify intracardiac structures, to control several surgical procedures, to document valve pathology, and to educate surgeons and operating room staff. Handling is easy and does not increase operative risk. Some procedures will be performed with minimal invasivity in future.