Furio Silvestri

Evidence That Human Cardiac Myocytes Divide after Myocardial Infarction

BACKGROUND The scarring of the heart that results from myocardial infarction has been interpreted as evidence that the heart is composed of myocytes that are unable to divide. However, recent observations have provided evidence of proliferation of myocytes in the adult heart. Therefore, we studied the extent of mitosis among myocytes after myocardial infarction in humans. METHODS Samples from the border of the infarct and from areas of the myocardium distant from the infarct were obtained from 13 patients who had died 4 to 12 days after infarction. Ten normal hearts were used as controls. Myocytes that had entered the cell cycle in preparation for cell division were measured by labeling of the nuclear antigen Ki-67, which is associated with cell division. The fraction of myocyte nuclei that were undergoing mitosis was determined, and the mitotic index (the ratio of the number of nuclei undergoing mitosis to the number not undergoing mitosis) was calculated. The presence of mitotic spindles, contractile rings, karyokinesis, and cytokinesis was also recorded. RESULTS In the infarcted hearts, Ki-67 expression was detected in 4 percent of myocyte nuclei in the regions adjacent to the infarcts and in 1 percent of those in regions distant from the infarcts. The reentry of myocytes into the cell cycle resulted in mitotic indexes of 0.08 percent and 0.03 percent, respectively, in the zones adjacent to and distant from the infarcts. Events characteristic of cell division--the formation of the mitotic spindles, the formation of contractile rings, karyokinesis, and cytokinesis--were identified; these features demonstrated that there was myocyte proliferation after myocardial infarction. CONCLUSIONS Our results challenge the dogma that the adult heart is a postmitotic organ and indicate that the regeneration of myocytes may be a critical component of the increase in muscle mass of the myocardium.

Spectrum of Clinicopathologic Manifestations of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: A Multicenter Study☆

OBJECTIVES The aim of the present investigation was to redefine the clinicopathologic profile of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC), with special reference to disease progression and left ventricular (LV) involvement. BACKGROUND Long-term follow-up data from clinical studies indicate that ARVC is a progressive heart muscle disease that with time may lead to more diffuse right ventricular (RV) involvement and LV abnormalities and culminate in heart failure. METHODS Forty-two patients (27 male, 15 female; 9 to 65 years old, mean [+/-SD] age 29.6 +/- 18) from six collaborative medical centers, with a pathologic diagnosis of ARVC at autopsy or heart transplantation, and with the whole heart available, were studied according to a specific clinicomorphologic protocol. RESULTS Thirty-four patients died suddenly (16 during effort); 4 underwent heart transplantation; 2 died as a result of advanced heart failure; and 2 died of other causes. Sudden death was the first sign of disease in 12 patients; the other 30 had palpitations, with syncope in 11, heart failure in 8 and stroke in 3. Twenty-seven patients experienced ventricular arrhythmias (ventricular tachycardia in 17), and 5 received a pacemaker. Ten patients had isolated RV involvement (group A); the remaining 32 (76%) also had fibrofatty LV involvement that was observed histologically only in 15 (group B) and histologically and macroscopically in 17 (group C). Patients in group C were significantly older than those in groups A and B (39 +/- 15 years vs. 20 +/- 8.8 and 25 +/- 9.7 years, respectively), had significantly longer clinical follow-up (9.3 +/- 7.3 years vs. 1.2 +/- 2.1 and 3.4 +/- 2.2 years, respectively) and developed heart failure significantly more often (47% vs. 0 and 0, respectively). Patients in groups B and C had warning symptoms (80% and 87%, respectively, vs. 30%) and clinical ventricular arrhythmias (73% and 82%, respectively, vs. 20%) significantly more often than patients in group A. Hearts from patients in group C weighed significantly more than those from patients in groups A and B (500 +/- 150 g vs. 328 +/- 40 and 380 +/- 95 g, respectively), whereas hearts from both group B and C patients had severe RV thinning (87% and 71%, respectively, vs. 20%) and inflammatory infiltrates (73% and 88%, respectively, vs. 30%) significantly more often than those from group A patients. CONCLUSIONS LV involvement was found in 76% of hearts with ARVC, was age dependent and was associated with clinical arrhythmic events, more severe cardiomegaly, inflammatory infiltrates and heart failure. ARVC can no longer be regarded as an isolated disease of the right ventricle.

The fate of acute myocarditis between spontaneous improvement and evolution to dilated cardiomyopathy: a review

The World Health Organization/International Society and Federation of Cardiology (WHO/ISFC) task force on the definition and classification of cardiomyopathies recently updated and reclassified heart muscle diseases.1 Myocarditis was defined as “an inflammatory disease of the myocardium . . . diagnosed by established histological, immunological, and immunohistochemical criteria.” Three distinct forms of inflammatory cardiomyopathy (that is, myocarditis associated with cardiac dysfunction) are recognised: idiopathic, autoimmune, and infectious. Various infectious factors may cause myocarditis, but viral agents, especially coxsackie group B viruses, are most commonly associated with this disease.2 Myocarditis has been recognised for almost two centuries, since Corvisart first described this disease in clinical terms in 1812,3 but in the last three decades there has been renewed interest in the inflammatory process in the myocardium. The reasons for this are multiple: the introduction of endomyocardial biopsy for in vivo diagnosis (the disease was often overdiagnosed in the past on purely clinical grounds)4; related efforts to produce standardised criteria for histological diagnosis (the Dallas criteria; fig 1)5; better understanding of cardiotropic viruses, studied in animal models of myocarditis,6 leading to new insights into the immunological mechanisms of the disease (fig2)7 and potential treatments in humans8; and lastly—and perhaps most interestingly—the finding of a possible causal relation between viral myocarditis and dilated cardiomyopathy,9 a major cause of congestive heart failure in western countries. Figure 1 Histological section of active lymphocytic myocarditis according to the Dallas criteria. A dense infiltrate of lymphocytes in close contact with damaged and necrotic myocytes is evident (haematoxylin and eosin × 100). Figure 2 CD4RO positive T lymphocytic cellular infiltrates in a diffuse pattern (× 40). Despite numerous published reports on this disease, the natural history of acute myocarditis is still poorly understood, despite the development of immunological …

Left ventricular involvement in right ventricular dysplasia

Right ventricular dysplasia, a heart muscle disease of unknown cause, anatomically characterized by variable replacement of myocardial muscle with adipose or fibroadipose tissue, is usually considered a selective disorder of the right ventricle. However, concomitant left ventricular involvement has been noted in a few cases. The aim of this study was to evaluate the prevalence and characteristics of left ventricular involvement in right ventricular dysplasia, as well as possible progression of the disease. Thirty-nine patients with right ventricular dysplasia were studied by M-mode and two-dimensional echocardiography; 28 of them also underwent cardiac catheterization, and in 25 endomyocardial biopsy was performed. On first examination the left ventricle was normal in 25 patients, whereas in the remaining 14 right ventricular abnormalities were associated with left ventricular involvement, characterized by asynergic areas (12 patients) or diffuse mild hypokinesis (two patients). During follow-up (27 patients, 84.1 +/- 66.1 months) 10 patients showed worsening of right ventricular function; in nine the appearance or worsening of left ventricular abnormalities was observed. Five patients died (four in congestive heart failure and one suddenly). Results of postmortem examination (available in two patients) showed atrophy of myocells and a massive fatty and fibrous infiltration of the right ventricular wall, associated with degenerative changes and fibrosis of the left ventricle. In conclusion, right ventricular dysplasia may be associated with left ventricular involvement and the disorder appears to be progressive in some instances.

Increased myocardial apoptosis in patients with unfavorable left ventricular remodeling and early symptomatic post-infarction heart failure

OBJECTIVES The purpose of this study was to evaluate a potential correlation between apoptotic rate (AR), post-infarction left ventricular (LV) remodeling, and clinical characteristics in subjects who died late (>or=10 days) after an acute myocardial infarction (AMI) with evidence of persistent occlusion of the infarct-related artery at autopsy. BACKGROUND Apoptosis contributes to myocardiocyte loss in cardiac disease and may have a pathophysiologic role in post-infarction LV remodeling. METHODS The AR was calculated at the site of infarction and in remote unaffected LV regions, using co-localization of in situ end labeling for deoxyribonucleic acid fragmentation and immunohistochemistry for caspase-3, in 14 subjects who died within two months after AMI. Correlation between AR and clinical characteristics such as age, site of AMI, transmural extension, multivessel coronary disease, and signs and/or symptoms of heart failure (HF), at the time of initial hospitalization for AMI or subsequently before death, was assessed using non-parametric statistical tests. Parameters of LV remodeling including diameters, free wall thickness, diameter-to-wall-thickness ratio, and mass were measured at gross examination at autopsy. Values are expressed as median (interquartile range). RESULTS Among clinical variables, early symptomatic post-infarction HF (9 cases, 64%) was associated with nearly fourfold increased AR at the site of infarction (26.2% [24.5% to 28.8%] vs. 6.4% [1.9% to 13.3%], p = 0.001). Moreover, AR both at the site of infarction and in unaffected regions was significantly correlated with parameters of progressive LV remodeling (p < 0.05). CONCLUSIONS Our data show that in patients dying >or=10 days after AMI, myocardial apoptosis is strongly associated with and may be a major determinant of unfavorable LV remodeling and early symptomatic post-infarction HF.

Magnetic resonance imaging in right ventricular dysplasia

Fifteen patients with right ventricular dysplasia were investigated by T1-weighted spin- and gradient-echo pulse sequences, using a protocol that enabled both a subjective analysis of myocardial signal intensity and a quantitative/qualitative analysis of right and left ventricular function. In 8 patients, 3 investigators independently recognized abnormally hyperintense areas in the anatomic sites usually affected by the disease. In 7 of these patients, these areas showed an overlap with a-dyskinetic areas imaged by both magnetic resonance imaging (MRI) and echocardiography. In 1 patient who underwent a cardiac transplant, MRI of the explanted heart showed an excellent correlation between the distribution of the lesions and the in vivo/in vitro features. The data were compared with those from an equivalent sample of patients affected by dilated cardiomyopathy. In the latter patients, no focal hyperintensities were attributed to any anatomic sites in the right ventricule, and no focal a-dyskinetic foci were observed. Furthermore, the 2 groups of patients were significantly different in regard to dimensional and functional quantitative parameters. The results suggest that MRI is useful in integrating echocardiographic data and can be helpful in diagnosing this disease in late stages.

Widespread Myocardial Inflammation and Infarct-Related Artery Patency

Background—Diffuse coronary vascular inflammation is associated with acute coronary syndromes. However, it is unknown whether inflammation also occurs within the myocardium. Therefore, this study was aimed at assessing the presence of activated cells in unaffected remote myocardium of patients with acute myocardial infarction (AMI), in comparison to the peri-infarct region from the same cases, and in comparison to myocardial specimens from control hearts. Methods and Results—Sixteen patients dying 1 to 12 weeks after AMI and 16 control subjects were selected at autopsy. Myocardial specimens were taken at remote unaffected viable regions and at peri-infarct regions in cases with AMI. Confocal microscopy was performed to measure the number of activated cells (DR+), T-lymphocytes (CD3+), and activated T-lymphocytes (CD3+/DR+). Activated cells and activated T-lymphocytes were found in remote unaffected regions in 11 of 16 cases (69%), in peri-infarct zone in all cases (100%), and in none of the control hearts (0%, P <0.001 versus others). A greater myocardial inflammatory burden in remote regions but not in peri-infarct regions was associated with persistent infarct-related artery occlusion (P <0.05). Conclusions—This study for the first time shows the presence of activated T-lymphocytes in remote unaffected myocardial regions in approximately two thirds of patients with recent AMI. Because these cells are associated with persistent infarct-related artery occlusion, our data may suggest that an antigenic stimulus present also in the myocardium triggers an immune response that may be critical to precipitate artery occlusion.

Persistent Infarct–Related Artery Occlusion Is Associated With an Increased Myocardial Apoptosis at Postmortem Examination in Humans Late After an Acute Myocardial Infarction

Background—Myocardial apoptosis persists beyond the acute phases of acute myocardial infarction (AMI) and is associated with left ventricular (LV) remodeling. Infarct-related artery (IRA) patency is considered a favorable prognostic factor after AMI and may be associated with more favorable LV remodeling because of reduced apoptosis at the site of AMI. The aim of this study was to assess the influence of IRA status on apoptotic rate (AR) in the hearts of subjects dying late after AMI. Methods and Results—We used colocalization for in situ end-labeling of DNA fragmentation and immunohistochemistry for caspase-3 to calculate the AR at time of death (12 to 62 days after AMI) in 16 hearts with persistently occluded IRAs and in 8 hearts with patent IRAs. No significant differences were found when comparing the clinical characteristics of the 2 groups. Occluded IRA was associated with significantly higher AR at site of infarction (25.8% [interquartile range 20.9% to 28.5%] versus 2.3% [interquartile range 0.6% to 5.0%], P <0.001). This strong correlation between IRA occlusion and AR remained statistically significant even after correction for clinical characteristics such as sex, age, history of previous additional AMI or heart failure, transmural AMI, anterior AMI, fibrinolytic treatment, time from AMI to death, trauma as cause of death, and multivessel coronary disease (P =0.003). Conclusions—A significantly higher AR was associated with persistent IRA occlusion late post-AMI. These data may suggest that the post-AMI benefits observed with a patent IRA (the “open-artery hypothesis”) may in part be due to reduced myocardial apoptosis.

Clinical and pathologic study of familial dilated cardiomyopathy

To evaluate the occurrence of familial cases of dilated cardiomyopathy (DC), 165 consecutive patients were studied. Diagnosis of myocardial disease was based on clinical, hemodynamic, bioptic, postmortem or a combination of these criteria. Twelve patients (7% of cases) showed evidence of myocardial disease in greater than or equal to 1 relative; 27 patients with myocardial disease were detected in the 12 families, but a suspected history of myocardial involvement was present in a further 16 cases. In 6 families proband and relatives were affected by DC (total 14 cases); in 1 of these families the disease began with an atrioventricular block. In 4 families the relatives showed the presence of myocarditis at the endomyocardial biopsy. In 2 families the relatives presented a right ventricular cardiomyopathy. The mode of inheritance was autosomal dominant in 7 families, recessive in 4; X-linked pattern may be hypothesized in 1. Nine patients died under the age of 45 years: 2 of sudden death, 6 of chronic heart failure and 1 of cerebral embolism. Familial transmission is not rare. Different modes of genetic transmission (autosomal dominant, recessive and X-linked) and different forms of myocardial disease suggest that familial DC may be a multifactorial disease.

Right precordial ST and QRS changes in the diagnosis of right ventricular infarction

Two groups of patients with anatomically proved acute myocardial infarction were compared in order to study specificity and sensitivity of the ECG criteria previously described in clinical and experimental right ventricular infarction ( RVI ). Group 1 included 21 patients with left inferior infarction and with a variable degree of right ventricular involvement; group 2 included nine patients with myocardial infarction confined to the left inferior wall. In both groups the presence of ST elevation (at least 0.05 mV) and the morphology of the QRS complex in V4R , V3R, and V1 were assessed in ECGs performed at the time of admission. Also, in order to evaluate the morphology of the ST segment and QRS complex in right precordial leads in normal subjects, an ECG with 12 standard and four right precordial leads ( V6R to V3R) was performed in 82 subjects (group 3) without clinical and ECG evidence of heart disease. Our data reveal that in normal subjects an rS pattern is always present in V3R and frequently (91%) in V4R . On the contrary, the presence of QS or QR complexes in both V4R and V3R are specific markers of right ventricular necrosis (specificity 100%; sensitivity 78%). The presence of injury and necrosis waves in V4R or V4R to V3R during inferior infarction is a useful diagnostic criterion in that it insures a highly specific diagnosis of acute RVI in the great majority (76 and 71%, respectively) of the cases with autopsy evidence of right ventricular involvement.