Prognostic determinants of hypertrophic cardiomyopathy--the results of the Shiga Cardiomyopathy Study

Sequential degradation of alphaII and betaII spectrin by calpain in glutamate or maitotoxin-stimulated cells

Calpain-catalyzed proteolysis of II-spectrin is a regulated event associated with neuronal long-term potentiation, platelet and leukocyte activation, and other processes. Calpain proteolysis is also linked to apoptotic and nonapoptotic cell death following excessive glutamate exposure, hypoxia, HIV-gp120/160 exposure, or toxic injury. The molecular basis for these divergent consequences of calpain action, and their relationship to spectrin proteolysis, is unclear. Calpain preferentially cleaves II spectrin in vitro in repeat 11 between residues Y1176 and G1177. Unless stimulated by Ca++ and calmodulin (CaM), betaII spectrin proteolysis in vitro is much slower. We identify additional unrecognized sites in spectrin targeted by calpain in vitro and in vivo. Bound CaM induces a second II spectrin cleavage at G1230*S1231. BetaII spectrin is cleaved at four sites. One cleavage only occurs in the absence of CaM at high enzyme-to-substrate ratios near the betaII spectrin COOH-terminus. CaM promotes II spectrin cleavages at Q1440*S1441, S1447*Q1448, and L1482*A1483. These sites are also cleaved in the absence of CaM in recombinant II spectrin fusion peptides, indicating that they are probably shielded in the spectrin heterotetramer and become exposed only after CaM binds alphaII spectrin. Using epitope-specific antibodies prepared to the calpain cleavage sites in both alphaII and betaII spectrin, we find in cultured rat cortical neurons that brief glutamate exposure (a physiologic ligand) rapidly stimulates alphaII spectrin cleavage only at Y1176*G1177, while II spectrin remains intact. In cultured SH-SY5Y cells that lack an NMDA receptor, glutamate is without effect. Conversely, when stimulated by calcium influx (via maitotoxin), there is rapid and sequential cleavage of alphaII and then betaII spectrin, coinciding with the onset of nonapoptotic cell death. These results identify (i) novel calpain target sites in both alphaII and betaII spectrin; (ii) trans-regulation of proteolytic susceptibility between the spectrin subunits in vivo; and (iii) the preferential cleavage of alphaII spectrin vs betaII spectrin when responsive cells are stimulated by engagement of the NMDA receptor. We postulate that calpain proteolysis of spectrin can activate two physiologically distinct responses: one that enhances skeletal plasticity without destroying the spectrin-actin skeleton, characterized by preservation of betaII spectrin; or an alternative response closely correlated with nonapoptotic cell death and characterized by proteolysis of betaII spectrin and complete dissolution of the spectrin skeleton.

Characteristics of a new repolarization descriptor substituted for T-wave morphology analysis in patients with cardiomyopathy and myocardial infarction

BACKGROUND

Total cosine R-to-T (TCRT) is a descriptor of T-wave morphology analysis based on singular value decomposition of 12-lead electrocardiograms (ECGs), which is useful in risk stratification of patients with myocardial infarction (MI). A new marker of standard ECG substituted for TCRT is proposed and the aim of this study was to evaluate the correlation between the new index and TCRT in patients with cardiomyopathy and MI.

METHODS AND RESULTS

Patients were divided into 2 groups: patients with cardiomyopathy (group CM, n=21, male =13), and patients with MI (group MI, n=36, male =28). TCRT was calculated using a custom software package. The ventricular gradient (VG)-index was defined as the total number of leads with opposite vectors for the QRS and T-wave. The value of TCRT was significantly lower in group CM than in group MI (-0.50+/-0.51 vs -0.04+/-0.65, p<0.01). The value for the VG-index was significantly greater in group CM than in group MI (5.9+/-3.4 vs 4.2+/-2.4, p<0.05). There was a significant correlation between TCRT and the VG-index in all of the patients (r(2)=0.47).

CONCLUSION

The VG-index is significantly correlated with TCRT, and both descriptors distinguish patients with MI from those with cardiomyopathy.

Proteolytic activation of protein kinase Calpha by peroxynitrite in stimulating cytosolic phospholipase A2 in pulmonary endothelium: involvement of a pertussis toxin sensitive protein

We sought to determine the roles of PKCalpha and G(i)alpha in regulating cPLA(2) activity in bovine pulmonary artery endothelial cell membrane under peroxynitrite (ONOO(-)) stimulation. Treatment of bovine pulmonary artery endothelial cells with ONOO(-) markedly stimulates the cell membrane associated protease activity, protein kinase C (PKC) activity, phospholipase A(2) (PLA(2)) activity, and arachidonic acid (AA) release from the cells. ONOO(-) significantly increases (Ca(2+))(i) in the cells, and pretreatment with the intracellular Ca(2+) chelator BAPTA-AM prevents the increase in (Ca(2+))(i), protease activity, PKC activity, and cPLA(2) activity in the cell membrane and AA release from the cells. Pretreatment of the cells with arachidonyl trifluoromethyl ketone (AACOCF(3)) (a cPLA(2) inhibitor) prevents ONOO(-)-stimulated cPLA(2) activity and AA release without producing a significant alteration of the protease activity. Pretreatment with vitamin E and aprotinin prevents ONOO(-)-induced increase in the protease activity, PKC activity, and cPLA(2) activity in the cell membrane and AA release from the cells. Pretreatment with the PKC inhibitor calphostin C prevents ONOO(-)-caused increase in PKC activity and cPLA(2) activity in the cell membrane and AA release from the cells. An immunoblot study of the cell membrane isolated from the ONOO(-)-treated cells with polyclonal PKCalpha antibody elicited an increase in the 80 kDa immunoreactive protein band along with an additional 47 kDa immunoreactive fragment. An immunoblot study with anti-nitrotyrosine antibody revealed that ONOO(-) induces nitration of tyrosine residues in PKCalpha. Pretreatment of the cells with aprotinin abolished the 47 kDa immunoreactive fragment in the immunoblot. An immunoblot study of the endothelial cell membrane with polyclonal cPLA(2) antibody revealed that treatment of the cells with ONOO(-) markedly increases the cPLA(2) immunoreactive protein profile in the membrane. Pretreatment of the endothelial cells with Go6976, a PKCalpha inhibitor, prevents the increase in PKC activity and cPLA(2) activity in the cell membrane under ONOO(-)-triggered condition. It, therefore, appears from the present study that treatment of the cells with ONOO(-) causes an increase in the protease activity, and that plays an important role in activating PKCalpha, which subsequently stimulates cPLA(2) activity in the cell membrane and AA release from the cells. An immunoblot assay with polyclonal G(i)alpha antibody elicited an immunoreactive band having a molecular mass of 41 kDa. Pretreatment of the cells with pertussis toxin markedly inhibits ONOO(-)-induced increase in cPLA(2) activity and AA release without significantly altering (Ca(2+))(i), protease activity, and PKC activity in the cell membrane. Treatment of the cells with ONOO(-) causes phosphorylation of G(i)alpha in the cell membrane, and pretreatment with Go6976 prevents its phosphorylation. We suggest the existence of a pertusssis toxin sensitive G protein-mediated mechanism for activation of cPLA(2) by ONOO(-) in bovine pulmonary artery endothelial cell membrane, which is regulated by PKCalpha-dependent phosphorylation and sensitive to aprotinin for its inhibition.

Is I-123-beta-methyl-p-iodophenyl-methylpentadecanoic acid imaging useful to evaluate asymptomatic patients with hypertrophic cardiomyopathy? I-123 BMIPP imaging to evaluate asymptomatic hypertrophic cardiomyopathy

PURPOSE

Myocardial imaging with I-123-beta-methyl-p-iodophenyl-methylpentadecanoic acid (BMIPP) is useful for predicting the outcome of patients with hypertrophic cardiomyopathy (HCM). But its usefulness in asymptomatic patients is unclear.

MATERIALS AND METHODS

Eighteen patients with asymptomatic HCM were examined with BMIPP and exercise stress perfusion imaging and then followed for 4.0 +/- 0.8 years. Extent of the defect (total defect score, TDS) and myocardial uptake of BMIPP (%uptake) were calculated to evaluate the BMIPP images.

RESULTS

In the first study abnormal findings in the BMIPP and perfusion images were detected of 67 and 22% of the patients, respectively. In the second BMIPP study, the TDS had increased (2.1 +/- 2.7 to 4.1 +/- 4.9, p < 0.005) and the %uptake had decreased (5.67 +/- 0.88% to 4.81 +/- 0.91%, p < 0.001), but there were no differences in myocardial perfusion between the first and second study. Exertional dyspnea developed in 17% of the patients, and they were among the one third of the patients with the greatest reduction of %uptake. This group also showed deterioration of left ventricular (LV) %fractional shortening and LV volume in the second study.

CONCLUSIONS

Abnormal findings on BMIPP images were frequently observed in patients with asymptomatic HCM, and these abnormal findings progressed with time. The greater reduction of %uptake during the follow-up period reflects the deterioration of the LV function.

Attenuation of biventricular pressure gradients by cibenzo-line in an 18-year-old patient with hypertrophic obstructive cardiomyopathy

An 18-year-old male patient with biventricular hypertrophic obstructive cardiomyopathy (HOCM) had successful reduction of the pressure gradients by cibenzoline. At 11 months after birth, he was first diagnosed with cardiac murmurs and by the age of 5 years, he was diagnosed with subpulmonic infundibular stenosis with a pressure gradient of 10 mmHg by cardiac catheterization. At the age of 14, re-catherterization revealed hypertrophic cardiomyopathy with isolated obstruction of the right ventricular outflow tract, with a pressure gradient of 70 mmHg, but no obstruction in the left ventricle. He began daily treatment with 30 mg propranolol. At the age of 18, he was admitted for cardiac evaluation. An echocardiogram revealed left mid-ventricular and subpulmonic obstructions associated with pressure gradients of 88 mmHg and 65 mmHg, respectively. A single oral dose of 200 mg of cibenzoline decreased the pressure gradients in the left and right ventricles (38 mmHg and 36 mmHg, respectively). He was then given 300 mg daily of cibenzoline, and both pressure gradients remained low without any complications 8 months later at the time of discharge.

Gender differences in the presentation of adult obstructive hypertrophic cardiomyopathy with resting gradient: a study of 122 patients

The present study investigated gender differences among adult patients with obstructive hypertrophic cardiomyopathy (OHCM) and resting gradient. Using outflow gradients >10 mmHg and the presence of asymmetrical septal hypertrophy of the left ventricle as inclusion criteria, 122 patients were identified among patients referred for echocardiographic examinations between May 1990 and October 1996. Clinical, echocardiographical and follow-up data were compared between male and female patients. The female patients were significantly older than male patients (mean age +/-SD 66.7+/-10.5 vs 54.8+/-12.5 years). The female patients had a smaller interventricular septal wall thickness, less frequent systolic anterior movement of the mitral valve, more frequent association with hypertension, and less frequent association with ischemic heart disease (IHD) and giant T wave inversion. In this study population, adult female patients presented with OHCM 12 years later than males. Whether this represents female patients' reluctance to seek medical attention early, a different disease process that affects predominantly elderly females, or a gender-specific end organ response to aging, hypertension, IHD and other processes, or the protective effects of estrogen remains to be determined.

The etiology of cardiac arrest in children and young adults: special considerations for ED management

Children and young adults rarely present to the emergency department (ED) in cardiac arrest. This review examines published series on nontraumatic, cardiac arrest for patients aged 1 to 45 years and discusses the differential diagnosis for cardiovascular collapse. Among the most common entities encountered are cardiac diseases (hypertrophic cardiomyopathy, myocarditis), airway diseases (pneumonia, epiglottitis, and asthma), epilepsy, hemorrhage (gastrointestinal bleeding, ectopic pregnancy), and drug toxicity (tricyclic antidepressants, cocaine). ED management of children and young adults in cardiac arrest requires an understanding of the heterogeneous pathophysiologic mechanisms and etiologies leading to cardiopulmonary dysfunction in these patients. The emergency physician should give particular focus to airway management for toddlers and preadolescents, because respiratory diseases predominate. When treating an adolescent or young adult, the resuscitation team should also consider toxic causes as well as occult hemorrhage. Management considerations unique to this patient population are discussed.