Haim Hammerman

Modelling the long QT syndrome with induced pluripotent stem cells

The ability to generate patient-specific human induced pluripotent stem cells (iPSCs) offers a new paradigm for modelling human disease and for individualizing drug testing. Congenital long QT syndrome (LQTS) is a familial arrhythmogenic syndrome characterized by abnormal ion channel function and sudden cardiac death. Here we report the development of a patient/disease-specific human iPSC line from a patient with type-2 LQTS (which is due to the A614V missense mutation in the KCNH2 gene). The generated iPSCs were coaxed to differentiate into the cardiac lineage. Detailed whole-cell patch-clamp and extracellular multielectrode recordings revealed significant prolongation of the action-potential duration in LQTS human iPSC-derived cardiomyocytes (the characteristic LQTS phenotype) when compared to healthy control cells. Voltage-clamp studies confirmed that this action-potential-duration prolongation stems from a significant reduction of the cardiac potassium current IKr. Importantly, LQTS-derived cells also showed marked arrhythmogenicity, characterized by early-after depolarizations and triggered arrhythmias. We then used the LQTS human iPSC-derived cardiac-tissue model to evaluate the potency of existing and novel pharmacological agents that may either aggravate (potassium-channel blockers) or ameliorate (calcium-channel blockers, KATP-channel openers and late sodium-channel blockers) the disease phenotype. Our study illustrates the ability of human iPSC technology to model the abnormal functional phenotype of an inherited cardiac disorder and to identify potential new therapeutic agents. As such, it represents a promising paradigm to study disease mechanisms, optimize patient care (personalized medicine), and aid in the development of new therapies.

Relation Between Red Cell Distribution Width and Clinical Outcomes After Acute Myocardial Infarction

Increased red blood cell distribution width (RDW) has been associated with adverse outcomes in heart failure and stable coronary disease. We studied the association between baseline RDW and changes in RDW during hospital course with clinical outcomes in patients with acute myocardial infarction (AMI). Baseline RDW and RDW change during hospital course were determined in 1,709 patients with AMI who were followed for a median of 27 months (range 6 to 48). The relation between RDW and clinical outcomes after hospital discharge were tested using Cox regression models, adjusting for clinical variables, baseline hemoglobin, mean corpuscular volume, and left ventricular ejection fraction. Compared to patients in the first RDW quintile, the adjusted hazard ratios for death progressively increased with higher quintiles of RDW (second quintile 1.1, 95% confidence interval [CI] 0.6 to 2.1; third quintile 1.8, 95% CI 1.0 to 3.2; fourth quintile 2.0, 95% CI 1.1 to 3.4; fifth quintile 2.8, 95% CI 1.6 to 4.7, p for trend <0.0001). An increase in RDW during hospital course was also associated with subsequent mortality (adjusted hazard ratio 1.13 for 1-SD increase in RDW, 95% CI 1.02 to 1.25). Similar results were obtained for the end point of heart failure. The association between increased RDW and worse outcome was evident in patients with and without anemia. In conclusion, there is a graded, independent association between increased RDW and mortality after AMI. An increase in RDW during hospitalization also portends adverse clinical outcome.

Fasting glucose is an important independent risk factor for 30-day mortality in patients with acute myocardial infarction: a prospective study.

Background—Stress hyperglycemia in patients with acute myocardial infarction has been associated with increased mortality. Most studies looked at the relationship between admission glucose (AG) and outcome; limited information is available about the clinical significance of fasting glucose (FG). Methods and Results—We prospectively studied the relationship between FG and 30-day mortality in 735 nondiabetic patients with acute myocardial infarction. FG (≥8-hour fast within 24 hours of admission) and AG were measured in each patient. At 30 days, 9 deaths (2%) occurred in patients with normal FG, and 11 (10%), 14 (13%), and 31 (29%) deaths occurred in the first, second, and third tertiles of elevated FG, respectively. Compared with normal FG (<110 mg/dL), the adjusted OR for 30-day mortality progressively increased with higher tertiles of elevated FG (first tertile, 4.6; 95% CI, 1.7 to 12.7; P=0.003; second tertile, 6.4; 95% CI, 2.5 to 16.6; P<0.0001; third tertile, 11.5; 95% CI, 4.7 to 20.0; P<0.0001). Compared with patients categorized as having normal AG (<140 mg/d), the adjusted ORs for tertiles of elevated AG were as follows: first tertile, 1.4 (95% CI, 0.5 to 3.8; P=0.54); second tertile, 3.0 (95% CI, 1.3 to 7.0; P=0.01); and third tertile, 4.4 (95% CI, 2.0 to 9.7; P<0.0001). Compared with patients with normal FG and AG, the adjusted ORs for 30-day mortality were 0.71 (95% CI, 0.15 to 3.4; P=0.67) in patients with elevated AG and normal FG, 3.4 (95% CI, 1.1 to 10.4; P=0.03) for patients with normal AG glucose and elevated FG, and 9.6 (95% CI, 3.5 to 26.0; P<0.0001) for patients with both elevated FG and AG. Comparing nested models showed that including AG failed to improve the prediction of the model based on FG (&khgr;2=5.4, 3 df, P=0.15). In contrast, the addition of FG classes to the model based on AG improved model prediction (&khgr;2=22.4, 3 df, P<0.0001). Conclusions—There is a graded relation between elevated FG and AG and 30-day mortality in patients with acute myocardial infarction. FG is superior to AG in the assessment of short-term risk. (Circulation. 2005;111:754-760.)

Dose-dependent effects of short-term methylprednisolone on myocardial infarct extent, scar formation, and ventricular function.

Etude faite chez le chien. Les doses eleves de methylprednisolone, mais pas les doses faibles, provoquent une cicatrice nettement moins epaisse, avec reduction de la fonction regionale, sans modification du contenu en collagene

Scar thinning due to ibuprofen administration after experimental myocardial infarction

Although much attention has been directed toward interventions which reduce myocardial infarct size, the effect of such agents on the healing phase of myocardial infarction is not well understood. The present study examines the effect of the nonsteroidal anti-inflammatory agent ibuprofen, previously demonstrated to be able to reduce infarct size, and of aspirin on the healing of experimentally produced myocardial infarcts. Thirty-nine anesthetized, open-chest dogs were subjected to proximal left anterior descending coronary artery occlusions for 6 weeks. Four groups of dogs were studied: (1) a control (untreated) group: (2) ibuprofen, 12.5 mg/kg intravenously 15 minutes and 6, 12, 18, and 24 hours after occlusion (high dose); (3) ibuprofen, 12.5 mg/kg intravenously 15 minutes and 3 hours after occlusion (low dose); (4) aspirin, 30 mg/kg intravenously 15 minutes and 3 hours after occlusion. The average thickness of the transmural scar and of the noninfarcted left ventricular wall was determined from multiple measurements of formalin-fixed left ventricular slices. The ratio of transmural scar to noninfarcted wall thickness was determined. In control animals the ratio was 0.87 with only 1 of 15 animals having a ratio less than 0.60. High-dose ibuprofen-treated animals had an average ratio of 0.59 (difference not significant [NS] compared with control values), with 6 of 9 animals having a ratio less than 0.60 (p less than 0.02 compared with control values). Low-dose ibuprofen-treated animals had an average ratio of 0.66 (p less than 0.05 compared with control values), with 4 of 8 animals having a ratio less than 0.60 (p = NS compared with control values). In the aspirin-treated animals, the ratio was 0.88 (p = NS compared with control values), with 0 of 7 animals having a ratio less than 0.60 (p = NS compared with control values). Although 1 of 22 animals had ratios less than 0.60 in the control and aspirin groups, 10 of 17 had ratios less than 0.60 in the ibuprofen-treated groups (p less than 0.001). Scars in treated animals did not differ from those in control animals histologically or by analysis of hydroxyproline content per unit weight. Thus, ibuprofen, a nonsteroidal anti-inflammatory agent which reduces infarct size, is shown to increase the incidence of scar thinning after myocardial infarction.

Impact of Red Blood Cell Transfusion on Clinical Outcomes in Patients With Acute Myocardial Infarction

Divergent views remain regarding the safety of treating anemia with red blood cell (RBC) transfusion in patients with acute coronary syndrome (ACS). We used a prospective database to study effect of RBC transfusion in patients with acute myocardial infarction (MI; n = 2,358). Cox regression models were used to determine the association between RBC transfusion and 6-month outcomes, incorporating transfusion as a time-dependent variable. The models adjusted for baseline variables, propensity for transfusion, and nadir hemoglobin previous to the transfusion. One hundred ninety-two patients (8.1%) received RBC transfusion. Six-month mortality rates were higher in patients receiving transfusion (28.1% vs 11.7%, p <0.0001). The adjusted hazard ratio (HR) for mortality was 1.9 in transfused patients (95% confidence interval [CI] 1.3 to 2.9). Interaction between RBC transfusion and nadir hemoglobin with respect to mortality (p = 0.004) was significant. Stratified analyses showed a protective effect of transfusion in patients with nadir hemoglobin < or=8 g/dL (adjusted HR 0.13, 95% CI 0.03 to 0.65, p = 0.013). By contrast, transfusion was associated with increased mortality in patients with nadir hemoglobin >8 g/dL (adjusted HR 2.2, 95% CI 1.5 to 3.3; p <0.0001). Similar results were obtained for the composite end point of death/MI/heart failure (p for interaction = 0.04). In conclusion, RBC transfusion in patients with acute MI and hemoglobin < or =8 g/dL may be appropriate. The increased mortality observed in transfused patients with nadir hemoglobin above 8 g/dL underscores the clinical difficulty of balancing risks and benefits of RBC transfusion in the setting of ACS.

Indomethacin-induced scar thinning after experimental myocardial infarction.

We investigated the effect of indomethacin, a widely used nonsteroidal antiinflammatory drug, on the healing of myocardial infarction (MI). Experimental MI was produced in anesthetized, openchest dogs by occluding the left anterior descending coronary artery. Ten dogs received indomethacin, 10 mg/kg i.v., and 11 received saline, 15 minutes and 3 hours after occlusion. After 6 weeks, the dogs were killed and their hearts were subjected to morphologic and biochemical analysis. The average thickness of the transmural scar and the noninfarcted left ventricular wall was measured at multiple sites in formalinfixed left ventricular slices and the ratio of the thickness of the transmural scar to the noninfarcted wall determined. The average thickness of the noninfarcted wall was 8.80 ± 0.19 mm (mean ± SEM) in the control group and 8.44 ± 0.26 mm in the indomethacin group (NS). The scar thickness was 7.24 ± 0.64 mm in the control group and 3.56 0.40 mm in the indomethacin group (p < 0.001). The ratio of scar to noninfarcted wall thickness was 0.83 ± 0.07 in the control group and 0.43 ± 0.04 in the indomethacin group (p < 0.001). Scars in treated dogs did not differ from controls either by light microscopic histologic analysis or by analysis of hydroxyproline content per unit weight. We conclude that indomethacin results in marked scar thinning when given early after experimental MI.

The impact of transient and persistent acute kidney injury on long-term outcomes after acute myocardial infarction

Acute kidney injury is a common complication of acute myocardial infarction and is generally associated with adverse outcomes. We studied the incidence and clinical significance of transient versus persistent acute kidney injury in 1957 patients who survived an ST-elevation acute myocardial infarction. We divided the patients into 5 groups based on changes in serum creatinine level during hospitalization. Mild acute kidney injury (creatinine 0.3-0.49 mg/dl above baseline) occurred in 156 patients and was transient (resolved during their hospital stay) in 61. Moderate/severe acute kidney injury (creatinine more than or 0.5 mg/dl above baseline) was found in 138 patients and was transient in 60. Compared to patients without acute kidney injury, the adjusted hazard ratio for mortality was 1.2 in patients with mild, transient acute kidney injury and 1.8 in patients with mild, persistent injury where the creatinine remained elevated. Patients with persistent moderate/severe acute kidney injury had the highest mortality (hazard ratio 2.4), whereas patients with transient moderate/severe injury had an intermediate risk (hazard ratio of 1.7). A similar relationship was present between acute kidney injury and admissions for heart failure. Our study shows that dynamic changes in renal function during acute myocardial infarction are strongly related to long-term mortality and heart failure.

Enhancement of salvage of reperfused myocardium by early beta-adrenergic blockade (timolol)

Although reperfusion of severely ischemic myocardium with thrombolytic agents or surgery has shown reduction in infarct size, the time after coronary occlusion during which reperfusion can salvage ischemic myocardium is limited. To determine whether beta-adrenergic blockade could enhance the salvage of ischemic myocardium by reperfusion, the left anterior descending coronary artery was occluded in 18 anesthetized dogs. An in vivo area at risk was determined by injecting technetium-99m-labeled albumin microspheres into the left atrium 5 minutes after occlusion and carrying out radioautography to define the poorly perfused tissue. Fifteen minutes after coronary occlusion, the dogs were randomized either to a control (saline-treated) group (n = 8) or to a timolol-treated group (n = 10). Timolol was administered until a decrease of 20% in heart rate or blood pressure occurred (mean total dose = 0.85 +/- 0.22 mg/kg +/- standard error of the mean). Coronary occlusion was maintained for 3 hours and was followed by 3 hours of reperfusion in both groups. At the end of 6 hours, infarct size was defined by triphenyltetrazolium chloride staining and masses of infarct and risk were calculated. Percent left ventricular mass at risk was similar for both groups (control = 20.9 +/- 2.4%, timolol-treated = 23.7 +/- 2.1%, p = not significant). Mass of necrosis/mass at risk was significantly smaller in the timolol-treated reperfusion group (27.3 +/- 2.7%) versus saline reperfusion alone (46.5 +/- 5.6%) (p less than 0.005). Thus, beta-adrenergic blockade administered early after coronary occlusion results in substantial enhancement of the salvage achieved by reperfusion alone.

Incidence of early left ventricular thrombus after acute anterior wall myocardial infarction in the primary coronary intervention era

BACKGROUND Rapid reperfusion has been shown to decrease mortality and improve left ventricular (LV) function. Previous studies have reported that LV thrombus (LVT) is a major complication of ST-segment elevation acute anterior wall myocardial infarction (AMI). There are little data on LVT in the current primary percutaneous coronary intervention (PPCI) era. We sought to demonstrate the incidence of LVT after AMI in patients treated with PPCI compared with those treated with thrombolysis or with conservative management. METHODS In a 6-year period, 642 patients with anterior wall AMI and echocardiography were treated with PPCI (n = 297), thrombolysis (n = 128), or conservative treatment (n = 217). Left ventricular thrombus was defined as an echodense mass adjacent to an abnormally contracting myocardial segment. RESULTS The rate of LVT among anterior wall AMI was 6.2%. Predictors for LVT were reduced ejection fraction (adjusted relative risk 0.71, 95% CI 0.52-0.96) and severe mitral regurgitation (adjusted relative risk 2.48, 95% CI 1.0-6.44). There was no statistical difference in LVT rate according to treatment: 21 (7.1%) of 297 patients in the PPCI group, 10 (7.8%) of 128 patients in the thrombolytic group, and 9 (4.1%) of 217 patients in the conservative group (P = .28). Those in the thrombolytic group were characterized by shorter duration from symptom onset and were generally also treated with heparin/low-molecular weight heparin. CONCLUSIONS This is the largest report to evaluate the incidence of LVT formation after AMI. In the current era of rapid reperfusion by PPCI, the rate of thrombus formation is similar to that reported in the past and not different than for patients currently treated conservatively or with thrombolysis.