Large MI Research Articles

GIANT MAGNETO-IMPEDANCE EFFECT OF MAGNETRON SPUTTERED Ni80Fe20/Cu COMPOSITE WIRES

In this work, Ni 80 Fe 20/ Cu composite wires of length 50 mm, consisting a Cu core of diameter 100 μm, coated with a layer of Ni 80 Fe 20, were produced by RF magnetron sputtering. To obtain a uniform coating, the wires were spun during sputtering by a homemade system. The results showed that the spinning speed might affect the maximum MI ratio and the magnetic properties. The MI ratio of the sputtered wires increases with the wire spinning speed in the magnetron sputtering. The film thickness had a significant effect on the magnitude and the optimum frequency of the giant magneto-impedance effect. The maximum MI ratio can reach about 247.4% for the specimen with a Ni 80 Fe 20 coating thickness of 2.81 μm at 400 kHz. This large MI effect, obtained at such low frequency range, was correlated with the electromagnetic interaction between the inner core and the magnetic coating.

Abstract 5570: β-2 Adrenergic Receptors Overexpression Promotes Angiogenesis in the Failing Myocardium through Activation of Vascular Endothelial Growth Factor/Akt Transduction Pathway

β-2 adrenergic receptor (β-2AR) plays a pivotal role in endothelial cell proliferation and promotes angiogenesis in response to hindlimb ischemia. Desensitization/uncoupling of cardiac β-2AR represents a well established phenomenon in heart failure (HF). In this study we aimed to investigate the role of β-2AR in the impairment of angiogenic processes occurring in the failing myocardium. To this purpose, we explored the angiogenic effects of β-2AR in a rat model of post-myocardial infarction (MI) HF. Cardiac adenoviral-mediated β-2AR overexpres-sion has been obtained via direct intramyocardial injection (4 x 10 11 PFU) 4 weeks after MI. We also extended our observation to β-2AR knockout (β2KO) mice developing HF after large anterior MI (infarct size 45 ± 6%). Cardiac β-2AR overexpression in HF rats markedly increased capillary and arteriolar length density, and induced larger left ventricular (LV) hypertrophic responses than that observed in untreated HF animals. Such LV adaptive remodelling was associated to reduced LV diameters and improved cardiac LV fractional shortening (FS) and +dP/dt. At molecular level, cardiac β-2AR gene transfer induced sustained activation of p-Akt and S6 kinase (S6K) phosphorylation and increased p-eNOS and VEGF levels that were instead reduced in untreated HF rats. In β2KO mice, we found a ~25% reduction of cardiac capillary and arteriolar density compared to WT mice. In β2KO mice, MI was associated with a dramatically higher 21-day mortality compared to WT (70% vs 30%, respectively). Survivors β2KO mice showed increased LV end diastolic and systolic diameters, and worse global cardiac contractility compared to controls. Cardiac Akt activation, S6K phosphorylation, p-eNOS, and VEGF-A production were significantly blunted in HF β2KO mice. Conclusions. β-2ARs play an important role in regulating angiogenic responses in post-MI HF hearts. The activation of Akt signal transduction pathway seems to be strongly involved in these mechanisms.

Percutaneous coronary intervention for major bifurcation lesions using the simple approach: risk of myocardial infarction

Recent data has suggested that simple (main vessel only) stenting is the preferred approach for patients with bifurcation lesions. We sought to determine the feasibility and outcomes of this approach in a year long inclusive registry. From August, 2004-2005, a registry of 1,600 consecutive patients undergoing PCI was reviewed. Patients undergoing PCI for major bifurcation lesions--> or =70% stenosis in a major (> or =2 mm) side branch and/or main vessel--were identified by review of the angiograms. Angiographic, clinical and treatment predictors of final SB compromise (> or =70% stenosis and/or less than TIMI 3 final flow) were identified. Hundred and fifty eight patients who underwent initial stenting of the main vessel with subsequent rescue of the side branch if SB compromise occurred ("Provisional Main Vessel Stenting") comprised the analysis population. Permanent SB compromise occurred in 16% of patients and was associated with an increased risk of large periprocedural MI and renal failure. Independent predictors of permanent SB compromise were lack of pre-PCI beta blockers, presence of diabetes mellitus, main vessel eccentric lesion and small SB vessel diameter. Among unselected patients with major bifurcation lesions undergoing a "simple" stenting approach, there is a significant rate of large periprocedural infarction and side branch compromise.

Giant magneto-impedance and skin effect in CuBe/CoNiP composite wires

The giant magneto-impedance and skin effect in electroless deposited CuBe/CoNiP composite wires with different diameter of CuBe core are presented, and involves a theoretical approach of the current density distributions in layers. Results show that the strong eddy current in the magnetic CoNiP coating will be induced due to the electromagnetic interactions with the CuBe core. It makes the skin effect strong in the magnetic coating even at very low frequency, and at this, large MI changes can also be observed.

First human randomized trial of G-CSF stem cell mobilization to treat large acute myocardial infarction—preliminary results of a pilot study

Based upon substantial preclinical testing, we initiated an FDA-sanctioned, single-site dose escalation study of granulocyte colony stimulation factor (G-CSF) to attempt to enhance myocardial healing for patients with large acute MI via mobilization of stem cells. Principal inclusion criteria were age ≤80 yrs, acute ST elevation MI reperfused late (4–48 h), EF 20–39%, and coronary anatomy unlikely to require CABG. Patients were randomized to G-CSF or placebo in a 2:1 fashion and treated for 5 days starting <48 h from MI onset. Initial daily SQ dose was 5 μg/kg day. Primary safety and efficacy endpoints are rupture-free survival and change in EF to 30 days. To date, six patients have been randomized. Final results of this pilot study will provide important information upon which to base further trials of G-CSF in the setting of acute MI.

Cardiovascular News

Cardiovascular News

Differential gene expression in infarct scar and viable myocardium from rat heart following coronary ligation.

Post-myocardial infarction (MI) remodeling of cardiac myocytes and the myocardial interstitium results in alteration of gross ventricular geometry and ventricular dysfunction. To investigate the mechanisms of the remodeling process of the heart after large MI, the expression of various genes in viable left ventricle and infarct scar tissue were examined at 16 weeks post-MI. Steady-state expression of Na(+)-K+ ATPase alpha-1 and -2, phospholamban (PLB), alpha-myosin heavy chain (alpha-MHC), ryanodine receptor (Rya) and Ca2+ ATPase (Serca2) mRNAs were decreased in the infarct scar vs noninfarcted sham-operated controls (P < 0.05). On the other hand, Gialpha2 and beta-MHC mRNAs were upregulated (P < 0.05, respectively) in the infarct scar whereas Na(+)-K+ ATPase-beta, Na(+)-Ca2+ exchanger and Gs mRNAs were not altered vs control values. In viable left ventricle, the alpha-1 subunit of Na(+)-K+ ATPase, alpha-3, beta-isoforms, Rya, beta-MHC, Gialpha2, Gs and Na(+)-Ca2+ exchanger were significantly elevated while expression of the alpha-2 subunit of Na(+)-K+ ATPase, PLB and Serca2 were significantly decreased compared to controls. Expression of CK2alpha mRNA was elevated in noninfarcted heart (145 +/- 15%) and diminished in the infarct scar (66 +/- 13%) vs controls. Expression of beta-MHC mRNA was elevated in both viable and infarct scar tissues of experimental hearts (140 +/- 31% and 183 +/- 30% vs. controls, respectively). These results suggest that cardiac genes in the infarcted tissue and viable left ventricle following MI are differentially regulated.

Effects of pre-, peri-, and postmyocardial infarction treatment with omapatrilat in rats: survival, arrhythmias, ventricular function, and remodeling

We showed previously that the vasopeptidase inhibitor (VPI) omapatrilat improves peri-myocardial infarction (MI) survival, but the mechanisms involved and whether these effects are sustained remained to be determined, and are the subject of this study. Rats (n = 272) received omapatrilat (20 mg x kg-1x day-1) starting 7 days before MI and continued peri- and post-MI, or no treatment (control). One group of rats had continuous ambulatory ECG and blood pressure recordings started 6 h before MI and continued until 24 h after MI, when survival was evaluated, and the rats were killed, and MI size was evaluated. A second group had left ventricular (LV) remodeling evaluated by echocardiography at 30 days and, at 38 days, had cardiac hemodynamics and morphology done and survival evaluated. Survival 24 h after MI (n = 255) improved with omapatrilat (60% vs. 46% for control; P = 0.0378). Over the next 37 days, there was no further improvement with omapatrilat but the early benefit was sustained. Omapatrilat reduced MI size 24 h after MI (36 +/- 2 vs. 42 +/- 2 mm2 for controls; P = 0.034). Omapatrilat reduced ventricular arrhythmia score 1-12 h after MI. Omapatrilat decreased blood pressure, but not during the first 24 h after MI. Omapatrilat reduced LV diastolic and systolic dimensions and LV and right ventricular weights compared with control large MI, indicating a decrease in reactive hypertrophy. Improvement in cardiac remodeling was accompanied by improved cardiac hemodynamics. Thus this study indicates that pre-, peri-, and post-MI treatment with the VPI omapatrilat is beneficial in survival, ventricular arrhythmias, LV remodeling, and cardiac function.

Effects of growth hormone following chronic angiotensin-converting enzyme inhibition in chronic heart failure: their relation to infarct size.

Growth hormone (GH) has been attracted as a possible adjunctive treatment for severe heart failure. However, its treatment effects have been still controversial. To assess severity of basal cardiac disease states in which GH might be effective, we analyzed the relation of treatment effects of GH following chronic angiotensin-converting enzyme (ACE) inhibition on cardiac function and structures to infarct size in rat model of chronic heart failure after myocardial infarction. One day after coronary occlusion, rats were randomized to either an ACE inhibitor, temocapril (T) (80 mg/L in drinking water) or placebo for 12 weeks. The animals received concomitant recombinant human (rh) GH (2 mg/kg/day, SC) (T + GH) or vehicle during the final 2 weeks. Compared with the T group, the T + GH group with large MI had smaller increments of left ventricular (LV) dP/dt(max) (0 vs 17%) and cardiac output (9 vs 49%), less improvement of LV relaxation (tau) (-3 vs 29%) and systemic vascular resistance (8 vs 29%), and a greater increase in LV end-diastolic pressure (123 vs -5%) than did the T+GH group with moderate MI. In the T + GH group when compared with the T group, these functional alterations were associated with a 12% reduction in the LV capillary density and a 21% increase in hydroxyproline contents in rats with large MI, whereas a 12% increase in the density and similar collagen contents were found in rats with moderate MI. Thus, prominent beneficial cardiovascular effects of the additive short-term, high-dose GH to chronic high-dose ACE inhibition were obtained in rats with moderate MI, whereas little additional benefit or even detrimental effects of GH were found in rats with large MI. The present study may provide an insight into the therapeutic strategy of GH given late after MI in the presence of chronic ACE inhibition in congestive heart failure.

Giant Magneto-Impedance Effect in Amorphous CoFeNiNbSiB Alloy Ribbon

The giant magneto-impedance (GMI) effects in amorphous Co70Fe4.5Ni4Nb1Si12.5B8 alloy ribbon have been observed. It is shown that the GMI effects increase with driving current frequency and an appropriate annealing can enhance the effect. A large MI ratio of about 120% in the as-cast sample and a ratio of about 400% in a suitably annealed sample have been measured at 5MHz.

Magnetic properties and giant magneto-impedance in amorphous FeNiCrSiB films

The giant magneto-impedance effect has been observed at room temperature in amorphous FeNiCrSiB films prepared by RF sputtering followed by an annealing treatment. The frequency spectra and field dependence of the effect are studied in the frequency range from 100 kHz to 13 MHz and the magnetic field range from 0 to 70 Oe. The longitudinal, transverse and perpendicular effects are observed in detail. A transverse magneto-impedance effect with a magnitude similar to the longitudinal case has been obtained, and a large perpendicular MI effect is also obtained. A maximum GMI ratio of about 38% is obtained at 13 MHz in the longitudinal and transverse cases. The field sensitivity of the longitudinal GMI is 3.4% at 13 MHz. A large perpendicular MI ratio of 11% is obtained at 11 MHz. The effect of annealing on the effective permeability and GMI is reported in this paper.

Ferromagnetic antiresonance in La0.7Ba0.3MnO3 traced out by temperature variation

Using the phenomenon of ferromagnetic antiresonance (FMAR) in ceramic samples of La0.67Ba0.33MnO3 at 10 GHz, we report a large magneto-impedance MI=Rs(H∥)−Rs(H⊥)]/Rs(H∥), where Rs is the microwave surface resistance and H the applied field. The MI reaches 30% at a field of 30 mT near room temperature. The FMAR also lets us measure M(T) by following Rs as a function of T and H.

Characterization of Marker Chromosomes in Namalva Cells by Chromosomal In Situ Suppression (CISS) Hybridization and R‐Banding

Chromosomal in situ suppression (CISS) hybridization was used to investigate the distribution of material of chromosomes 1 and 5 present in marker chromosomes of Namalva cells. The Namalva cell line, established from a Burkitt's lymphoma, exhibits a highly variable female karyotype with a large number of marker chromosomes. Libraries from sorted human chromosomes 1 and 5 were used to delineate material of these chromosomes present in the Namalva karyotype. We used the DAB/peroxidase reaction and reflection contrast microscopy for detection of biotinylated hybrid molecules. Identification of chromosomes was achieved by fluorescent R-banding after CISS hybridization, which allowed the assignment of hybridized regions to the particular marker chromosomes. After CISS hybridization with a chromosome I library, the normal chromosome I was labelled as well as a large marker MI and the long arm of marker M3. Using a chromosome 5 library it could be shown that the distal part of the long arm of one chromosome 5 was translocated to marker M2. The normal chromosome 5 was completely labelled. The present investigation demonstrates the advantage of combining CISS hybridization and banding for the identification of complex, rearranged tumor karyotypes.

急性心筋梗塞の剖検例における初発梗塞と再発梗塞の心電図所見および梗塞巣の位置関係

Sixty-four elderly autopsy cases with acute myocardial infarction (AMI) were investigated in Nagoya Koseiin Geriatric Hospital. First AMI was observed in 35 cases, and recurrent AMI in 29. The primary causes of death were cardiac rupture and congestive heart failure in the first AMI and the recurrent AMI, respectively. The most frequent ECG findings before AMI were ischemic ST-T-change (57%) and Q-QS abnormality (41%) on the first and recurrent AMI, respectively. The ECG findings were normal in 6 (21%) of 29 recurrent MI cases. There was a tendency towards Q-QS abnormality in large size old MI, but not in small size MI. In 29 cases with recurrent AMI, the positional relationship between the old MI and the AMI was classified into 3 groups of different area, same area, and different and same area according to the Maccarie classification. The frequency in our cases was similar in the 3 groups. Ten cases with different area were further classified into 3 groups, i.e. opposite, adjacent, and opposite and adjacent. Opposite cases consisted of 4 (40%) cases, while opposite and adjacent consisted of 6 (60%). It is suggested that the recurrent AMI is more likely to be fatal when AMI occurs opposite to a previous lesion rather than adjacent to an old lesion.

The electrocardiographic diagnosis of acute myocardial infarction in the thrombolytic era

The 12-lead ECG remains a simple and inexpensive technique to diagnose AMI in its early phases. The diagnostic accuracy of the ECG depends upon the extent of myocardial necrosis and its localization. The ECG is most sensitive in patients with occlusion of the LAD artery, followed by the RCA and the left CFA. In 10% to 20% of patients with AMI the initial ECG either shows nonspecific changes or is normal. The correlation between the ECG and infarct-related artery varies according to the involved vessel. Classic ECG changes are seen in 90% of the LAD artery, in 70% to 80% of RCA, and in only 50% of CFA occlusions. A second important issue is the mechanism and clinical significance of reciprocal ST segment changes, which usually indicate larger MI, more impaired ventricular function, worse prognosis, and in some patients, significant disease of a noninfarct-related artery. Furthermore, the value of the ECG in estimating myocardial injury and infarct size remains controversial. The ECG plays an important role in coronary reperfusion. ST segment elevation is one of the principal criteria for instituting thrombolytic therapy, and helps predict those who will most likely benefit from coronary reperfusion. The role of the ECG in evaluating the reperfusion status after coronary thrombolysis is not clear. Rapid return to baseline or normalization of the ST segment suggests opening of the occluded vessel, though a small or negligible change does not exclude successful reperfusion.

Rhabdomyolysis and Myoglobinuric Renal Failure following Cardioversion and CPR for Acute MI

A 50-year-old man suffered an MI with VFIB at work, and efforts at resuscitation were initiated immediately. Ninety minutes of CPR and 14 cardioversions were given by trained personnel before VFIB converted to sinus rhythm. Reversible myoglobinuric renal failure ensued, requiring two weeks of hemodialysis. Scanning with technetium-99m pyrophosphate revealed extensive muscle injury in the regions of cardioversion and a large anterolateral MI. Prolonged resuscitative efforts involving repeated cardioversion may predispose to myoglobinuric renal failure.

Relation of peak creatine kinase levels during acute myocardial infarction to presence or absence of previous manifestations of myocardial ischemia (angina pectoris or healed myocardial infarction)

The hypothesis that acute myocardial infarction (Ml) is more extensive in patients without previous angina or healed MI was evaluated in 177 patients with documented recent acute MI. Ninety-nine patients (56%) had no previous angina or healed MI (negative history group), and the remaining 78 patients (44%) had a previous history of angina or healed MI (positive history group). The mean peak creatine kinase (CK) level in the negative history group was 784 compared with 419 IU in the positive history group (p < 0.0001). The mean peak CK-MB level in the negative history group was 128 compared with 76 IU in the positive history group (p < 0.001). The mean peak CK-MB level was higher in the negative history group after controlling for age, streptokinase administration, previous coronary artery bypass grafting or treatment with β-blocking agents. Despite the high frequency of healed MI in the positive history group (73%), the rates of in-hospital complications were similar for the 2 groups. Patients with acute MI without previous angina or healed MI have substantially higher peak CK and CK-MB levels; this implies a larger MI than in patients with previous angina or healed MI.

Cardiocirculatory adjustments to exercise following myocardial infarction in rats.

The sequential changes of the cardiocirculatory response to exercise over time in rats with myocardial infarction and failure were studied. Hemodynamics and regional blood flow (RBF, radioactive microspheres) were determined at rest and during exercise either at 1, 10 or 42 days after infarction (MI, infarct size 41.4 +/- 2.6% of LV) or sham procedures (SH). Whereas the response to exercise was attenuated one day after surgery in MI and SH, cardiocirculatory recovery was present in SH at 10 days and LV systolic and end-diastolic pressures separated SH and MI groups. Renal vasoconstriction during exercise occurred 10 days after MI and BF to working muscle during exercise was significantly lower in MI as compared to SH. At 42 days after MI manifest heart failure was present and despite significant blood flow redistribution (p less than 0.05 MI vs SH in renal and cutaneous beds) impaired skeletal muscle flow was observed along with increased vascular resistance in working muscle during exercise. We conclude that the cardiocirculatory response to exercise following large MI follows a distinctive time-dependent pattern, which differs from that observed at rest. Besides exaggerated sympathetically mediated vasoconstriction during exercise, impaired vasodilatation in skeletal muscle at exercise emerged.