Clinical disease presentation and ECG characteristics of LMNA mutation carriers.

OBJECTIVE: Mutations in the LMNA gene encoding lamins A and C of the nuclear lamina are a frequent cause of cardiomyopathy accounting for 5-8% of familial dilated cardiomyopathy (DCM). Our aim was to study disease onset, presentation and progression among LMNA mutation carriers. METHODS: Clinical follow-up data from 27 LMNA mutation carriers and 78 patients with idiopathic DCM without an LMNA mutation were collected. In addition, ECG data were collected and analysed systematically from 20 healthy controls. RESULTS: Kaplan-Meier analysis revealed no difference in event-free survival (death, heart transplant, resuscitation and appropriate implantable cardioverter-defibrillator therapy included as events) between LMNA mutation carriers and DCM controls (p=0.5). LMNA mutation carriers presented with atrial fibrillation at a younger age than the DCM controls (47 vs 57 years, p=0.003). Male LMNA mutation carriers presented with clinical manifestations roughly a decade earlier than females. In close follow-up non-sustained ventricular tachycardia was detected in 78% of LMNA mutation carriers. ECG signs of septal remodelling were present in 81% of the LMNA mutation carriers, 21% of the DCM controls and none of the healthy controls giving a high sensitivity and specificity for the standard ECG in distinguishing LMNA mutation carriers from patients with DCM and healthy controls. CONCLUSIONS: Male LMNA mutation carriers present clinical manifestations at a younger age than females. ECG septal remodelling appears to distinguish LMNA mutation carriers from healthy controls and patients with DCM without LMNA mutations.

Increased ventilatory response to exercise in symptomatic and asymptomatic LMNA mutation carriers: a follow-up study.

BACKGROUND: LMNA mutations are an important cause of cardiomyopathy often leading to cardiac arrhythmias, heart failure and even heart transplantation. An increasing number of asymptomatic mutation carriers are identified, as family members of the index patients are screened. Our aim was to study the disease progression in asymptomatic LMNA mutation carriers and in patients with symptomatic cardiolaminopathy by repeated spiroergometric testing in a prospective clinical follow-up study. METHODS AND RESULTS: We studied 26 LMNA mutation carriers once a year during 5 years up to 6 times by spiroergometry, clinical assessment, laboratory tests and echocardiography. The 23 control subjects underwent clinical assessment and spiroergometry once. Twelve of the mutation carriers were asymptomatic, and 14 had some clinical manifestations of the mutation ranging from clinically relevant rhythm disturbances to DCM and heart failure. Compared to controls, the symptomatic carriers showed a higher slope of the ventilatory equivalent for CO2 (V˙E/V˙CO2 slope) and a lower fraction of end-tidal CO2 (FetCO2 ). The asymptomatic mutation carriers also showed an increased ventilatory response to exercise during the follow-up as indicated by increased V˙E/V˙CO2 slope and decreased FetCO2 . CONCLUSIONS: The study suggests that an increased ventilatory response during exercise might reveal a preclinical manifestation of DCM in LMNA mutation carriers.

Effects of angiotensin II blockade on cardiomyocyte regeneration after myocardial infarction in rats.

INTRODUCTION: We studied the effects of angiotensin type 1 receptor blockade (ARB) on formation of new cardiomyocytes, neovascularization and ventricular remodelling after myocardial infarction (MI). METHODS: Male Wistar rats with MI or sham-operated controls were treated with either losartan or vehicle. Bromodeoxyuridine (BrdU) was given to identify newly formed cardiac cells. Immunohistochemical analysis was used to quantify proliferative and apoptotic cardiomyocytes, vascular structures and c-Kit+ stem/progenitor cells, western blotting to evaluate gene expression, and planimetry and echocardiography to assess cardiac structure and function. RESULTS: The number of BrdU+ cardiomyocytes increased similarly in the vehicle and losartan treated MI groups. The number of apoptotic or proliferating cardiomyocytes did not differ between losartan and vehicle treated rats. Losartan induced an increase in capillary and BrdU+ vascular densities in the infarct border zone. Losartan treatment completely prevented post-MI cardiac hypertrophy. In the non-infarcted myocardium the amount of all BrdU+ cells (including non-cardiomyocyte cells) was highest in the vehicle treated MI rats at week 4. CONCLUSIONS: The number of newly formed cardiomyocytes increased after MI. Angiotensin II blockade neither stimulated nor prevented cardiomyocyte regeneration. ARB treatment increased vascular densities in the infarct border zone and modulated remodelling of the non-infarcted myocardium preventing effectively post-MI cardiac hypertrophy.

Characteristics of atrial fibrillation and comorbidities in familial atrial fibrillation.

INTRODUCTION: One-third of lone atrial fibrillation (AF) presents as familial disorder. Heterogeneity of both genetic background and clinical manifestations remains largely uncharacterized. We aimed to evaluate the clinical characteristics and especially the triggering factors of familial AF. METHODS AND RESULTS: Probands were screened from 84 consecutive lone AF patients seen in our tertiary hospital arrhythmia clinic. Those confirmed to have at least 1 first-degree relative with lone AF were included. 12-lead ECG, Holter recording, and cardiac ultrasound were performed. Data concerning arrhythmias and other medical history were collected. Altogether 17 kindreds with 59 AF patients, 52 of whom had lone AF, were identified. Initiation of AF was atrial extrasystolia (PACs) related in 35%, and vagal or sympathetic in 30% of cases. Within any given family, the characteristics related to AF initiation were the same in two-thirds of kindreds. AV conduction abnormalities were found in 2 families, sinus node dysfunction in 2 families, and both in 3 families. Frequent premature ventricular complexes (>1,000/24 hours) were observed in 9 families. Additional comorbidities included dilative cardiomyopathy and sudden death in 3 families. CONCLUSIONS: In familial AF the proportion of PACs-related AF is lower than expected. The arrhythmia triggers for lone AF in general are heterogeneous but often family specific. Concomitant rhythm disorders, as well as cardiomyopathies, are common in patients with familial AF. A positive family history for AF in an apparently lone AF patient may be a marker for wider spectrum of cardiac pathology.

Pregnancy and childbirth in carriers of the lamin A/C-gene mutation.

This retrospective case report describes 11 pregnancies in five women. All of the women were carriers of the lamin A/C gene mutation known to cause dilated cardiomyopathy, often together with atrioventricular conduction disturbances. The penetrance of these mutations is age-dependent but almost complete. We found no major adverse effects or worsening in the cardiac condition during or after the pregnancy in these patients. All babies were healthy except for one with a small ventricular septal defect, one diagnosed with tracheobronchomalasia, and one with a patent ductus arteriosus. None of these defects have been associated with lamin A/C mutations.

Activation of protective and damaging components of the cardiac renin-angiotensin system after myocardial infarction in experimental diabetes.

INTRODUCTION: Diabetes is associated with prolonged apoptotic cell death of cardiac myocytes and adverse remodelling after myocardial infarction (MI). Because the renin-angiotensin system (RAS) has a major role in the remodelling, we studied whether diabetes is associated with altered regulation of RAS after MI in rats. METHODS: Male Wistar rats were randomised to receive either streptozotocin (diabetic group) or citrate buffer (control group) intravenously. MI was produced four weeks later by ligating the left descending coronary artery. The rats were sacrificed 1, 4 and 12 weeks after the operation. Angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE 2), angiotensin type 1 and 2 receptors (AT(1)-receptor, AT(2)-receptor), and connective tissue growth factor (CTGF) mRNA expression were determined. RESULTS: The expression of both protective and damaging components of RAS increased after MI. However, myocardial ACE 2 and AT(2)-receptor messenger ribonucleic acid (mRNA) expression levels were significantly lower in diabetic compared to non-diabetic rats 1 week after MI. In contrast, AT(1)-receptor, ACE and CTGF mRNA levels were up-regulated in diabetic as compared with non-diabetic rats 12 weeks after MI. CONCLUSION: The activation of the protective components of RAS (ACE 2 and AT(2)-receptor) was blunted early after MI in diabetic rats, whereas the levels of ACE, AT(1)-receptor and CTGF mRNA leading to adverse effects on myocardium, were elevated in diabetic as compared with non-diabetic rats. This unbalanced activation of the RAS may influence the pathophysiology of myocardial injury in diabetes after MI.

Vasopeptidase inhibition has beneficial cardiac effects in spontaneously diabetic Goto-Kakizaki rats.

In this study we examined diabetes- and hypertension-induced changes in cardiac structure and function in an animal model of type 2 diabetes, the Goto-Kakizaki (GK) rat. We hypothesized that treatment with omapatrilat, a vasopeptidase inhibitor, which causes simultaneous inhibition of angiotensin converting enzyme and neutral endopeptidase, provides additional cardioprotective effects, during normal- as well as high sodium intake, compared to treatment with enalapril, a selective inhibitor of angiotensin converting enzyme. Fifty-two GK rats were randomized into 6 groups to receive either normal-sodium (NaCl 0.8%) or high-sodium (NaCl 6%) diet and enalapril, omapatrilat or vehicle for 12 weeks. The GK rats developed hypertension, cardiac hypertrophy and overexpression of cardiac natriuretic peptides and profibrotic connective tissue growth factor compared to nondiabetic Wistar rats. The high dietary sodium further increased the systolic blood pressure, and changed the mitral inflow pattern measured by echocardiography towards diastolic dysfunction. Enalapril and omapatrilat equally decreased the systolic blood pressure compared to the control group during normal- as well as high-sodium diet. Both drugs had beneficial cardioprotective effects, which were blunted by the high dietary sodium. Compared to enalapril, omapatrilat reduced the echocardiographically measured left ventricular mass during normal-sodium diet and improved the diastolic function during high-sodium diet in GK rats. Furthermore, omapatrilat reduced relative cardiac weight more effectively than enalapril during high sodium intake. Our results suggest that both the renin-angiotensin and the neutral endopeptidase system are involved in the pathogenesis of diabetic cardiomyopathy since vasopeptidase inhibition was shown to provide additional benefits in comparison with selective angiotensin converting enzyme inhibition alone.

Cardioprotective effects of vasopeptidase inhibition vs. angiotensin type 1-receptor blockade in spontaneously hypertensive rats on a high salt diet.

The aim of our study was to compare the cardioprotective effects of vasopeptidase inhibition with those of angiotensin type 1 (AT1)-receptor blockade, a diuretic and the combination of AT1-receptor blockade and a diuretic in an experimental rat model of essential hypertension on a high salt diet. Spontaneously hypertensive rats (SHR) (n =73) were divided into 6 groups to receive the following diet and drug regimens for 8 weeks: 1) low salt controls (NaCl 0.5%); 2) high salt controls (NaCl 6%); 3) omapatrilat (40 mg/kg/d) on a high salt diet; 4) losartan (30 mg/kg/d) on a high salt diet; 5) hydrochlorothiazide (HCTZ; 10 mg/kg/d) on a high salt diet; and 6) losartan+HCTZ (30+10 mg/kg/d) on a high salt diet. Blood pressure was measured by tail-cuff plethysmography. The histological score of myocardial damage, myocardial collagen volume fraction (CVF), connective tissue growth factor (CTGF) expression and cardiomyocyte apoptosis were determined. As an antihypertensive, omapatrilat showed greater efficacy than monotherapy with losartan or HCTZ, and was equally effective as the combination of losartan+HCTZ. Assessed by myocardial damage score, omapatrilat and losartan protected cardiac morphology better than HCTZ or the drug combination. Omapatrilat decreased CVF to a greater extent than the other therapies, whereas losartan was most effective in decreasing CTGF expression. All drug treatments, except HCTZ, decreased cardiomyocyte apoptosis. Our findings provide evidence that both vasopeptidase inhibition and AT1-receptor blockade exert cardioprotective properties beyond their blood pressure-lowering effects. Cardioprotection was associated with prevention of cardiomyocyte apoptosis and inhibition of extracellular matrix formation.

Effect of vasopeptidase inhibitor omapatrilat on cardiomyocyte apoptosis and ventricular remodeling in rat myocardial infarction.

We have shown earlier that cardiomyocyte apoptosis continues at a high level late after myocardial infarction and contributes to adverse cardiac remodeling. Here we studied whether this process can be inhibited by the vasopeptidase inhibitor omapatrilat, a drug which causes simultaneous inhibition of both angiotensin converting enzyme and neutral endopeptidase. Our hypothesis was that omapatrilat-treated rats would have less cardiomyocyte apoptosis, and less adverse cardiac remodeling compared to rats treated with selective inhibitors of angiotensin converting enzyme, neutral endopeptidase or placebo. Myocardial infarction was produced by ligation of the left anterior descending coronary artery. Rats were randomized to receive omapatrilat, captopril, neutral endopeptidase inhibitor SQ-28603 or vehicle. Rats treated with omapatrilat and captopril had reduced cardiac BNP mRNA levels and less myocardial fibrosis by comparison with the vehicle-treated rats. However, omapatrilat was more effective than captopril in attenuating hypertrophy as measured by relative cardiac weight (3.0+/-0.2 vs. 3.8+/-0.2 mg/g, P<0.01) or by echocardiographically determined left ventricular mass (0.61+/-0.05 vs. 0.83+/-0.06 g, P<0.01). Myocardial apoptosis was elevated both in the infarction border zone (0.129+/-0.017%) and in the remote area (0.035+/-0.005%) still 4 weeks after myocardial infarction. Angiotensin converting enzyme inhibition proved to be important in the prevention of apoptosis since both omapatrilat and captopril reduced the number of apoptotic myocytes whereas selective neutral endopeptidase inhibitor SQ-28603 had no effect. In conclusion, myocardial apoptosis, remaining increased 4 weeks after myocardial infarction, was reduced by angiotensin converting enzyme inhibition. Vasopeptidase inhibition was more effective than selective angiotensin converting enzyme inhibition in preventing adverse cardiac remodeling after myocardial infarction.

Expression of heme oxygenase-1 in response to myocardial infarction in rats.

Heme oxygenase-1 (HO-1) is a heat shock protein catalysing the degradation of heme to yield biliverdin, carbon monoxide and iron. Several recent studies have proposed the stress-inducible HO-1 to participate in cellular protection also in the heart. We, therefore, examined the expression and localization of HO-1 in a rat experimental myocardial infarction model. Male Wistar rats were subjected to left anterior coronary artery ligation or sham-operation and sacrificed at 1 day, 1 week and 4 weeks after ligation. The expression of HO-1 mRNA was assessed by real-time quantitative RT-PCR and the localization of HO-1 protein by immunoconfocal microscopy. At day 1, HO-1 mRNA was increased 3.9-fold in the peri-infarct border area vs sham-operated hearts (P<0.001) and 2.9-fold vs remote areas of the same hearts (P<0.001). At 1 week, HO-1 mRNA levels remained significantly higher (5-fold) in the peri-infarct border area than in sham-operated hearts (P<0.001). In addition, HO-1 mRNA transiently increased 1.6-fold in the remote non-infarcted myocardium vs sham operated hearts (P<0.05). HO-1 mRNA returned to basal levels by 4 weeks. The increase in HO-1 mRNA was accompanied by increased immunoreactivity of HO-1 protein in the vascular walls throughout the myocardium, and in the cardiomyocytes and fibroblast-like cells of the peri-infarct border areas. Cardiomyocytes showed immunoreactivity at the intercalated disc area, and in the sarcoplasmic reticulum as indicated by the striated pattern of staining. The results suggest that the induction of HO-1 may have an important role in the heart during the first days after myocardial infarction.