Improved Utilization of Serial Testing Without Increased Admissions after Implementation of High-Sensitivity Troponin I: a Controlled Retrospective Cohort Study

BACKGROUND

Guidelines recommend high-sensitivity cardiac troponin (hs-cTn) for diagnosis of myocardial infarction. Use of hs-cTn is increasing across the U.S., but questions remain regarding clinical and operational impact. Prior studies have had methodologic limitations and yielded conflicting results.

OBJECTIVE

To evaluate the impact of transitioning from conventional cardiac troponin (cTn) to hs-cTn on test and resource utilization, operational efficiency, and patient safety.

DESIGN

Retrospective cohort study in two New York City hospitals during the months before and after transition from conventional cTn to hs-cTn at Hospital 1. Hospital 2 served as a control.

PARTICIPANTS

Consecutive emergency department (ED) patients with at least one cTn test resulted.

INTERVENTION

Multifaceted hs-cTn intervention bundle, including a 0/2-h diagnostic algorithm for non-ST-elevation myocardial infarction, an educational bundle, enhancements to the electronic medical record, and nursing interventions to facilitate timed sample collection.

MAIN MEASURES

Primary outcomes included serial cTn test utilization, probability of hospital admission, ED length of stay (LOS), and among discharged patients, probability of ED revisit within 72 h resulting in hospital admission. Multivariable regression models adjusted for age, sex, temporal trends, and interhospital differences.

KEY RESULTS

The intervention was associated with increased use of serial cTn testing (adjusted risk difference: 48 percentage points, 95% CI: 45-50, P < 0.001) and ED LOS (adjusted geometric mean difference: 50 min, 95% CI: 50-51, P < 0.001). There was no significant association between the intervention and probability of admission (adjusted relative risk [aRR]: 0.99, 95% CI: 0.89-1.1, P = 0.81) or probability of ED revisit within 72 h resulting in admission (aRR: 1.1, 95% CI: 0.44-2.9, P = 0.81).

CONCLUSIONS

Implementation of a hs-cTn intervention bundle was associated with an improvement in serial cTn testing, a neutral effect on probability of hospital admission, and a modest increase in ED LOS.

Antioxidant effects on hypoxia-induced oxidative stress and apoptosis in rat rotator cuff fibroblasts

Most cells, highly sensitive to oxygen levels, undergo apoptosis under hypoxia. Therefore, the involvement of hypoxia in rotator cuff tendon degeneration has been proposed. While previous studies have reported that hypoxia induces apoptosis in rotator cuff fibroblasts (RCFs), little research has investigated whether antioxidants have cytoprotective effects against RCF apoptosis. The present study aimed at determining whether the antioxidant N-acetylcysteine (NAC) exerted cytoprotective effects against hypoxia-induced RCF apoptosis. Third-passage rat RCFs were divided into normoxia, NAC, hypoxia and NAC-hypoxia groups. The hypoxia inducer was 1,000 µmol/L cobalt chloride (CoCl2); the antioxidant was 20 mmol/L NAC. Expressions of hypoxia-inducible factor-1α (HIF-1α) and heme oxygenase-1 (HO-1), cell viability, intracellular reactive oxygen species (ROS) production, apoptosis rates as well as expressions of cleaved caspase-3, cleaved poly ADP-ribose polymerase-1 (PARP-1), vascular endothelial growth factors-β (VEGF-β) and matrix metalloproteinase-2 (MMP-2) were evaluated. Expression of HIF-1α and HO-1 was significantly higher in the hypoxia group than in the normoxia group (p < 0.001). Cell viability was significantly lower in the hypoxia group than in the normoxia group (p < 0.001). Intracellular ROS production, apoptosis rate and expressions of cleaved caspase-3, cleaved PARP-1, VEGF-β and MMP-2 were significantly higher in the hypoxia group than in the normoxia group (p < 0.001). All these responses were significantly attenuated by pre-treatment with NAC (p ≤ 0.001). ROS were involved in hypoxic RCF apoptosis induced by CoCl2; NAC, an ROS scavenger, inhibited hypoxia-induced RCF apoptosis by inhibiting ROS production.

Efficacy and safety of direct oral anticoagulants in patients with atrial fibrillation and chronic kidney disease

BACKGROUND

Direct oral anticoagulants (DOACs) are effective alternatives to warfarin for stroke prevention in patients with atrial fibrillation (AF) including patients with CKD III. However, data on patient outcomes with DOACs for advanced CKD are limited, while warfarin use is controversial.

METHODS

A retrospective study of patients with AF using DOACs and CKD stages III-V was conducted. The primary outcomes were stroke or systemic embolism and major bleeding while on DOAC therapy among CKD IV and V patients. Rates of outcomes from the DOAC trials and from previous studies of warfarin in CKD were referenced.

RESULTS

Of 316 patients reviewed, 152 were included with mean CrCl of 38.8 mL/min. Stroke and systemic embolism occurred at a rate of 1.17 per 100 person-years, with no significant difference between CKD IV/V and CKD III (P = .567). Rates were comparable to DOAC use from the DOAC trials, and lower than rates in studies of warfarin in CKD IV/V patients. There was a nonstatistically significant trend toward increased major bleeding in CKD IV/V patients. Rates of major bleeding in CKD III to V subjects were comparable to published rates for warfarin users with similar levels of renal impairment.

CONCLUSIONS

In our study, DOACs appeared to be as efficacious and safe in CKD IV and V as in CKD III. In addition, DOACs appeared to be more effective than, and as safe as warfarin when compared with reference studies of patients with advanced CKD. Our findings support the use of DOACs for thromboembolism prevention in patients with advanced CKD and AF.

P1021Comparative efficacy of microfidelity technology vs standard ablation for atrioventricular nodal ablation

Background

Microfidelity Cateter Technology has proven efficacy in ablating atrial arrhythmias in multiple pilot studies. Closely spaced radial microelectrodes render a focused near-field electrogram. Case series suggest that this catheter design facilitates accurate ablations with fewer radiofrequency (RF) lesions. Atrioventricular junction (AVJ) ablation is regarded as a straightforward procedure, but case records show wide variance in procedure times and number of RF lesions required.

Methods

Twenty-four patients scheduled for AVJ ablation were randomized to treatment with either the Microfidelity technology or standard 8mm/8 French ablation catheter. Both groups located the AVJ by fluoroscopic landmarks and His electrograms, and the MiFi group used electroanatomical mapping to create the location of his electrograms. The primary endpoints were development of Junctional Rhythm (JR) or Complete Heart Block (CHB), and time from first RF lesion until rhythm change. Secondary endpoints included number of RF applications.

Results

Patients were randomized one-to-one to the MiFi arm or standard ablation arm. JR or CHB was achieved in all patients. Time from first RF lesion until JR/CHB was: (Median/IQR) 325 sec/250–1270 sec. vs 287 sec/101–406 sec. Number of RF applications was 5/3–15 applications vs 4.5/1–5 applications. Total procedure time in the lab was 134 min/73.5–172.5 min vs 58 min/52–146 min.

Microfidelity Technology vs Standard

Conclusion

Analysis suggests that the MiFi catheter is efficacious in ablating the AVJ, but requires greater RF duration and number of lesions, with wider case-by-case variability to achieve JR or CHB. Microfidelity technology and electroanatomical mapping did not result in faster time to completion than using fluoroscopic landmarks and His electrograms alone. Preoperative choice of sheath for catheter stability and contact may also play a role in a more efficient timely successful ablation of the AV node.

Acknowledgement/Funding

Boston Scientific

87Effects of the chymase inhibitor fulacimstat on adverse cardiac remodelling after acute myocardial infarction - Results of the CHIARA MIA 2 trial

Introduction

Adverse cardiac remodelling represents the most important risk factor for the development of heart failure (HF) after myocardial infarction (MI). Chymase is a protease that generates locally pro-fibrotic factors such as angiotensin II, TGFβ, and matrixmetallproteases that contribute to tissue remodelling.

Purpose

This phase IIa study examined the effects of the chymase inhibitor fulacimstat on functional parameters of adverse cardiac remodelling after acute MI.

Methods

A double-blind, multinational, randomized, placebo-controlled study was performed in patients after first STEMI who were treated with primary percutaneous coronary intervention within 24h of symptom onset. To enrich for patients at risk of adverse remodelling, main inclusion criteria were a left-ventricular ejection fraction (LVEF)≤45% and an infarct size>10% on day 5 to 9 post MI as measured by cardiac MRI. On day 6 to 12 post MI, patients were randomized to treatment with either 25 mg fulacimstat (n=54) or placebo (n=53) twice daily on top of standard of care. The changes in LVEF, LVEDVI, and LVESVI from baseline to 6 months of treatment were analyzed by a central blinded cardiac MRI core laboratory.

Results

Fulacimstat was safe and well tolerated, 64.8% of patients treated with fulacimstat and 75.5% of patients treated with placebo reported treatment emergent adverse events. Fulacimstat achieved exposures that were approximately 10-fold higher than those predicted to be required for minimal therapeutic activity. After six months of treatment, there were no effects of fulacimstat compared to placebo on the changes in LVEF, LVEDVI, and LVESVI (see Table).

Analysis of primary efficacy parameters Parameter Placebo Fulacimstat p-value LVEF (%) baseline 37.2±6.1 39.1±5.5 0.15 6 months 41.2±8.4 42.6±8.4 0.45 delta 4.0±5.0 3.5±5.4 0.69 LVEDVI (mL/m2) baseline 80.0±17.1 77.4±18.2 0.51 6 months 85.1±19.1 84.7±23.4 0.94 delta 5.1±18.9 7.3±13.3 0.54 LVESVI (mL/m2) baseline 50.5±13.0 47.3±12.3 0.26 6 months 51.1±16.9 49.6±18.1 0.71 delta 0.6±14.8 2.3±11.2 0.56 Data are given as mean ± standard deviation.

Conclusion

Fulacimstat was safe and well tolerated in patients with left-ventricular dysfunction (LVD) after first STEMI but had no effect on adverse cardiac remodelling in the experimental setting of this study.

Acknowledgement/Funding

The study was funded by its sponsor BAYER AG

Atrial fibrillation and chronic kidney disease: A review of options for therapeutic anticoagulation to reduce thromboembolism risk

Atrial fibrillation and chronic kidney disease (CKD) commonly occur together, which poses a therapeutic dilemma due to increased risk of both systemic thromboembolism and bleeding. Chronic kidney disease also has implications for medication selection. The objective of this review is to evaluate the options for anticoagulation for thromboembolism prevention in patients with atrial fibrillation and chronic kidney disease. We searched PubMed for studies of patients with atrial fibrillation and CKD on warfarin or a direct oral anticoagulant (DOAC) for thromboembolism prevention through January 1 2018, in addition to evaluating major trials evaluating DOACs and warfarin use as well as society guidelines. For patients with mild to moderate chronic kidney disease, primarily observational data supports the use of warfarin, and high quality trial data and meta-analyses support the use and possible superiority of DOACs. For patients with severe chronic kidney disease, there are limited data on warfarin which supports its use, and data for DOACs is limited primarily to pharmacologic studies which support dose reductions but lack information on patient outcomes. For patients with end-stage renal disease, studies on warfarin are conflicting, but the majority suggest a lack of benefit and possible harm; studies in DOACs are very limited, but apixaban is the least renally cleared and may be both safe and effective. In conclusion, warfarin or DOACs may be used based on the degree of severity of chronic kidney disease, but further study in needed in patients with end-stage renal disease.

Systematic Review for the 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

BACKGROUND

Although large randomized clinical trials have found that primary prevention use of an implantable cardioverter-defibrillator (ICD) improves survival in patients with cardiomyopathy and heart failure symptoms, patients who receive ICDs in practice are often older and have more comorbidities than patients who were enrolled in the clinical trials. In addition, there is a debate among clinicians on the usefulness of electrophysiological study for risk stratification of asymptomatic patients with Brugada syndrome.

AIM

Our analysis has 2 objectives. First, to evaluate whether ventricular arrhythmias (VAs) induced with programmed electrostimulation in asymptomatic patients with Brugada syndrome identify a higher risk group that may require additional testing or therapies. Second, to evaluate whether implantation of an ICD is associated with a clinical benefit in older patients and patients with comorbidities who would otherwise benefit on the basis of left ventricular ejection fraction and heart failure symptoms.

METHODS

Traditional statistical approaches were used to address 1) whether programmed ventricular stimulation identifies a higher-risk group in asymptomatic patients with Brugada syndrome and 2) whether ICD implantation for primary prevention is associated with improved outcomes in older patients (>75 years of age) and patients with significant comorbidities who would otherwise meet criteria for ICD implantation on the basis of symptoms or left ventricular function.

RESULTS

Evidence from 6 studies of 1138 asymptomatic patients were identified. Brugada syndrome with inducible VA on electrophysiological study was identified in 390 (34.3%) patients. To minimize patient overlap, the primary analysis used 5 of the 6 studies and found an odds ratio of 2.3 (95% CI: 0.63-8.66; P=0.2) for major arrhythmic events (sustained VAs, sudden cardiac death, or appropriate ICD therapy) in asymptomatic patients with Brugada syndrome and inducible VA on electrophysiological study versus those without inducible VA. Ten studies were reviewed that evaluated ICD use in older patients and 4 studies that evaluated unique patient populations were identified. In our analysis, ICD implantation was associated with improved survival (overall hazard ratio: 0.75; 95% confidence interval: 0.67-0.83; P<0.001). Ten studies were identified that evaluated ICD use in patients with various comorbidities including renal disease, chronic obstructive pulmonary disease, atrial fibrillation, heart disease, and others. A random effects model demonstrated that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.72; 95% confidence interval: 0.65-0.79; P<0.0001), and a second "minimal overlap" analysis also found that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.61-0.82; P<0.0001). In 5 studies that included data on renal dysfunction, ICD implantation was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.60-0.85; P<0.001).

Decreased Rates of Inpatient Hypoglycemia Following Implementation of an Automated Tool in the Electronic Medical Record for Identifying Root Causes

OBJECTIVE

The objective was to identify root causes of hypoglycemia on medicine inpatient units using an automated tool. Data collected will guide educational interventions aimed at improving patient care and safety by decreasing rates of hypoglycemia.

METHODS

A survey was conducted among RNs to identify risk factors for hypoglycemia. Survey data were used to create a hypoglycemia root cause survey tool in the EMR. RNs were prompted to utilize the tool when blood glucose (BG) < 70 mg/dL. Once the most common modifiable cause of hypoglycemia was identified, an educational intervention for safe and effective use of insulin was launched. This strategy was designed to empower the care team to reduce the insulin dose when appropriate to prevent future hypoglycemic episodes.

RESULTS

BG data were compared from March and April in 2016 and 2017. Rates of hypoglycemia (BG < 70 mg/dL) decreased from 2.3% to 1.5%; BG values in target range (70-180 mg/dL) increased from 59.4% to 65.7%; hyperglycemia (BG > 180 mg/dL) decreased from 38.3% to 32.8% (all P values < .001). The number of patients with recurrent hypoglycemia (3 or more episodes) decreased from 5.7% to 2.2% ( P = .044).

CONCLUSIONS

The two most frequent modifiable causes of hypoglycemia (insulin and nutrition) were identified by an RN survey and confirmed by chart review. A targeted educational intervention addressing safe and effective insulin dosing resulted in a significant decrease in both hypoglycemia and recurrent hypoglycemia. This was associated with an improvement in overall glycemic control. Ongoing clinician education regarding insulin and nutrition accompanied by discussions between RNs and prescribers to address hypoglycemic events in real-time could continue to lower the rate of occurrence.

Systematic review for the 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

BACKGROUND

Although large randomized clinical trials have found that primary prevention use of an implantable cardioverter-defibrillator (ICD) improves survival in patients with cardiomyopathy and heart failure symptoms, patients who receive ICDs in practice are often older and have more comorbidities than patients who were enrolled in the clinical trials. In addition, there is a debate among clinicians on the usefulness of electrophysiological study for risk stratification of asymptomatic patients with Brugada syndrome.

AIM

Our analysis has 2 objectives. First, to evaluate whether ventricular arrhythmias (VAs) induced with programmed electrostimulation in asymptomatic patients with Brugada syndrome identify a higher risk group that may require additional testing or therapies. Second, to evaluate whether implantation of an ICD is associated with a clinical benefit in older patients and patients with comorbidities who would otherwise benefit on the basis of left ventricular ejection fraction and heart failure symptoms.

METHODS

Traditional statistical approaches were used to address 1) whether programmed ventricular stimulation identifies a higher-risk group in asymptomatic patients with Brugada syndrome and 2) whether ICD implantation for primary prevention is associated with improved outcomes in older patients (>75 years of age) and patients with significant comorbidities who would otherwise meet criteria for ICD implantation on the basis of symptoms or left ventricular function.

RESULTS

Evidence from 6 studies of 1138 asymptomatic patients were identified. Brugada syndrome with inducible VA on electrophysiological study was identified in 390 (34.3%) patients. To minimize patient overlap, the primary analysis used 5 of the 6 studies and found an odds ratio of 2.3 (95% CI: 0.63-8.66; p=0.2) for major arrhythmic events (sustained VAs, sudden cardiac death, or appropriate ICD therapy) in asymptomatic patients with Brugada syndrome and inducible VA on electrophysiological study versus those without inducible VA. Ten studies were reviewed that evaluated ICD use in older patients and 4 studies that evaluated unique patient populations were identified. In our analysis, ICD implantation was associated with improved survival (overall hazard ratio: 0.75; 95% confidence interval: 0.67-0.83; p<0.001). Ten studies were identified that evaluated ICD use in patients with various comorbidities including renal disease, chronic obstructive pulmonary disease, atrial fibrillation, heart disease, and others. A random effects model demonstrated that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.72; 95% confidence interval: 0.65-0.79; p<0.0001), and a second "minimal overlap" analysis also found that ICD use was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.61-0.82; p<0.0001). In 5 studies that included data on renal dysfunction, ICD implantation was associated with reduced all-cause mortality (overall hazard ratio: 0.71; 95% confidence interval: 0.60-0.85; p<0.001).

Multidisciplinary approach in the management of a complicated crown root fracture

BACKGROUND

This article describes the management of a complicated crown root fracture.

CASE REPORT

A young patient presented with a crown root fracture of the maxillary left central incisor with an oblique subgingival fracture line. A multidisciplinary treatment approach including endodontic treatment, orthodontic extrusion, surgical extraction and intra-alveolar repositioning was used to gain sufficient crown length of the fractured maxillary incisor. The coronally repositioned maxillary left central incisor was stabilised by sutures and a resin wire splint. A resin core was built up followed by fabrication of an all-ceramic crown. Clinical and radiographic follow-up of the maxillary left central incisor after 24 months showed no signs of bone resorption or pathology and good aesthetics and functions were maintained.

Cardiologist concordance with the American College of Cardiology appropriate use criteria for cardiac testing in patients with coronary artery disease

The American College of Cardiology Appropriate Use Criteria (AUC) were developed to guide use of myocardial perfusion single-photon emission computed tomography (MPS), stress echocardiography, and cardiac computed tomographic angiography (CCTA). To date, cardiologist application of AUC from a patient-based multiprocedure perspective has not been evaluated. A Web-based survey of 15 clinical vignettes spanning a wide spectrum of indications for MPS, STE, and CCTA in coronary artery disease was administered to cardiologists who rated the ordered test as appropriate, inappropriate, or uncertain by AUC application and suggested a preferred alternative imaging procedure, if any. In total 129 cardiologists responded to the survey (mean age 49.5 years, board certification for MPS 65%, echocardiography 39%, CCTA 32%). Cardiologists agreed with published AUC ratings 65% of the time, with differences in all categories (appropriate, 50% vs 53%; inappropriate, 42% vs 20%; uncertain, 9% vs 27%, p <0.0001 for all comparisons). Physician age, practice type, or board certification in MPS or echocardiography had no effect on concordance with AUC ratings, with slightly higher agreement for those board certified in CCTA (68% vs 64%, p = 0.04). Cardiologist procedure preference was positively associated with active clinical interpretation of MPS and CCTA (p = 0.03 for the 2 comparisons) but not for ownership of the respective imaging equipment. In conclusion, cardiologist agreement with published AUC ratings is generally high, although physicians classify more uncertain indications as inappropriate. Active clinical interpretation of a procedure contributes most to increased procedure preference.

Diagnostic accuracy of coronary computed tomography angiography as interpreted on a mobile handheld phone device

OBJECTIVES

This study assessed the diagnostic performance of coronary computed tomography angiography (CTA) for the detection and exclusion of significant coronary artery stenosis as remotely interpreted on a mobile handheld device with dedicated medical imaging software.

BACKGROUND

Recent advances in technology now permit remote interpretation of medical imaging studies on mobile handheld devices, although the diagnostic performance of this approach is unknown.

METHODS

We evaluated 102 patients with stable chest pain and both 64-detector row coronary CTA and quantitative invasive coronary angiography. The diagnostic performance of remote coronary CTA interpretation was assessed using a mobile handheld device and employing dedicated software. The coronary CTA studies were examined in an intent-to-diagnose manner for the presence or absence of coronary artery stenosis > or =50% on a per-artery and per-patient level; results were compared with quantitative invasive coronary angiography. Two blinded imagers independently interpreted coronary CTA studies, with a third imager achieving consensus for discordance. Coronary CTAs were re-interpreted in random order to determine interobserver agreement. Finally, coronary CTAs were evaluated on a dedicated 3-dimensional imaging workstation; results were compared to mobile handheld device findings for intertechnology agreement.

RESULTS

The prevalence of significant coronary artery stenosis was 25% (26 of 102) at the per-patient level and 10% (40 of 405) at the per-artery level. Per-patient and per-artery sensitivity, specificity, and positive and negative predictive values were: 100% (26 of 26), 78% (59 of 76), 60% (26 of 43), and 100% (59 of 59), respectively; and 95% (38 of 40), 85% (310 of 365), 41% (38 of 93), and 99% (310 of 312), respectively. At the per-artery level, interobserver, intraobserver, and intertechnology agreement was 0.74, 0.89, and 0.75, respectively (p < 0.01 for all).

CONCLUSIONS

The interpretation of coronary CTA using a mobile handheld device with dedicated software for medical image evaluation possesses high diagnostic accuracy for detection and exclusion of significant coronary stenosis.

Management and clinical outcomes of acute cardiac tamponade complicating electrophysiologic procedures: a single-center case series

BACKGROUND

Cardiac perforation with tamponade is an infrequent occurrence during an electrophysiologic procedure. The customary approach to management includes volume resuscitation followed by pericardiocentesis. Such a procedure, however, is not without its own risk, especially when performed emergently. We hypothesized that some patients experiencing this type of complication can be managed successfully in a conservative fashion, without the need for an additional invasive procedure.

METHODS

We retrospectively analyzed the clinical outcomes and echocardiographic features of 33 consecutive patients who experienced this complication during cardiac electrophysiology (EP) procedures performed at our institution from 1988 to 2007. Nineteen patients (58%) were managed conservatively with intravenous fluids and vasopressors (Group A). Fourteen patients (42%) were managed invasively with pericardiocentesis (Group B).

RESULTS

The mean systolic blood pressure at diagnosis did not differ between the two groups (64 vs 71 mmHg, P = 0.134). The mean lengths of hospitalization (4.7 vs 4.9 days, P = 0.75) and survival to hospital discharge (100% in both groups) were also similar. A large pericardial effusion (>or=2 cm) was seen predominantly among Group B patients. There was a statistically significant temporal trend toward managing this type of complication invasively (P = 0.038).

CONCLUSION

Among patients who experience cardiac perforation as an acute complication of EP procedure, there appears to be a role for conservative management in a subset of patients who do not have echocardiographic evidence of a large effusion and who respond well to initial stabilizing measures consisting of fluids and vasopressors.

Safety of gadoversetamide in patients with acute and chronic myocardial infarction

PURPOSE

To assess the safety data from two large, multicenter, phase 2 trials on the use of gadoversetamide (OptiMARK, Tyco Healthcare/Mallinckrodt, St. Louis, MO) as a contrast agent in delayed hyperenhancement magnetic resonance imaging (DE-MRI) in patients with acute and chronic myocardial infarction (MI).

MATERIALS AND METHODS

The study population from both trials comprised 577 patients who were randomly assigned to one of four dose groups (0.05, 0.1, 0.2, or 0.3 mmol/kg) before undergoing DE-MRI. Safety evaluations included physical and electrocardiographic (ECG) examinations. Vital signs, laboratory values, adverse events (AE), and serious adverse events (SAE) were monitored before and after contrast administration.

RESULTS

Of the 577 patients who received gadoversetamide, 124 (21.5%) reported a total of 164 AEs; most were mild (139 AEs; 84.8%) or moderate (25 AEs; 15.2%). ECG-related changes were the most frequent AE. Site investigators judged only eight AEs as likely related to gadoversetamide and only two of the eight as clinically relevant. Further evaluation suggested neither AE was related to gadoversetamide. Two SAEs were reported, but none was judged related to gadoversetamide by the site investigators.

CONCLUSION

Gadoversetamide is safe for use in patients with acute or chronic MI up to a dose of 0.3 mmol/kg.

"Lots of clots": multiple thromboemboli including a huge paradoxical embolus in a 29-year old man

Paradoxical embolism occurs when a venous thrombus passes into the arterial circulation, most commonly through an intracardiac shunt. This phenomenon has been associated with catastrophic outcomes such as stroke and ischemic limb. We report the case of a 29-year old man with multiple thromboemboli including a deep venous thrombus, bilateral pulmonary emboli, and a paradoxical embolus into his left subclavian artery. We postulate the underlying predisposition and sequence of events that may have resulted in these multiple blood clots and report on his successful surgical outcome.

Evaluation of prosthetic valve endocarditis by 64-row multidetector computed tomography

Two patients with prosthetic aortic valves--one bioprosthetic and one mechanical--presented with bacteremia and underwent evaluation for infective prosthetic valve endocarditis. Multidetector computed tomography (MDCT) imaging demonstrated vegetations on both prosthetic valves confirmed by transesophageal echocardiography. Based on the MDCT coronary artery assessment, neither patient underwent pre-operative invasive coronary angiography. Both patients underwent surgical treatment without complication. In conclusion, this report demonstrates that MDCT can, in some cases, accurately image vegetations on prosthetic aortic valves in infective endocarditis.

Clinical and Electrophysiological Spectrum of Idiopathic Ventricular Outflow Tract Arrhythmias

OBJECTIVES

This study sought to compare and contrast the clinical and electrophysiological characteristics of outflow tract arrhythmias.

BACKGROUND

Idiopathic ventricular outflow tract arrhythmias manifest clinically in 3 forms: 1) paroxysmal sustained monomorphic ventricular tachycardia (SMVT), 2) repetitive nonsustained ventricular tachycardia (NSVT), or 3) premature ventricular contractions (PVCs). Although these arrhythmias have a similar site of origin, it is unknown whether they share a common mechanism or similar clinical features.

METHODS

A total of 127 patients (63 female [50%], mean age 51 +/- 15 years) were evaluated for outflow tract arrhythmias.

RESULTS

A total of 36 (28%) presented with the index clinical arrhythmia of SMVT, 46 (36%) with NSVT, and 45 (35%) with PVCs. The sites of origin of the arrhythmias were similar among the 3 groups, occurring in the right ventricular outflow tract in 82%. Sustained ventricular tachycardia was more likely to be induced during exercise in the SMVT (10 of 15 patients [67%]) than NSVT or PVCs groups (p < 0.01). Sustained outflow tract ventricular tachycardia was induced at electrophysiology study in 78% of SMVT patients, 48% of NSVT patients, and 4% of PVCs patients. Adenosine was similarly effective in all 3 groups (p = NS).

CONCLUSIONS

Patients with outflow tract arrhythmias can be differentiated based on the subtype of arrhythmia. However, the observation that approximately 50% of patients with NSVT and approximately 5% of patients with PVCs have inducible sustained ventricular tachycardia that behaves in an identically unique manner to those who present with sustained ventricular tachycardia (e.g., adenosine-sensitive) suggests that rather than representing distinct entities, outflow arrhythmias may be considered a continuum of a single mechanism.

Comparison of a Standard versus Accelerated Dosing Regimen for d,l-Sotalol for the Treatment of Atrial and Ventricular Dysrhythmias

BACKGROUND

The current recommended starting dose of sotalol is 80 mg orally twice per day, followed by a judicious increase in dosage every 3 days under continuous telemetry monitoring. We hypothesized that sotalol administered at a higher starting dose (120 or 160 mg twice daily) would allow a more rapid attainment of therapeutic response with an acceptable safety and comparable efficacy profile.

METHODS

Two hundred nine inpatients with various atrial and ventricular dysrhythmias were begun on either a standard starting dose (80 mg b.i.d.) or an accelerated dose (120 or 160 mg b.i.d.) of sotalol. In-hospital occurrences of drug-related adverse effects (proarrhythmic and others), drug efficacy, and length of hospitalization were retrospectively compared between the two groups.

RESULTS

Ten patients (9.3%) in the 80 mg b.i.d. starting dose group experienced a cardiac adverse effect of sotalol as compared to 15 patients (14.9%) in the accelerated dose group (P = 0.286). The mean amount of corrected QT (QTc) prolongation over baseline was not significantly different between the two groups at hospital discharge (22.5 ms vs 21.6 ms, P = 0.898). There was a trend toward more noncardiac side effects of sotalol in the accelerated dose group: 2 (1.9%) versus 7(6.9%), P = 0.092. The average length of hospital stay was similar in the two groups (6.8 days vs 7.4 days, P = 0.558).

CONCLUSION

Initiating sotalol at 120-160 mg orally twice per day marginally increases the risk of cardiac and non-cardiac side effects compared to the standard starting regimen of 80 mg b.i.d. Such an accelerated dosing regimen neither shortened hospitalization nor had any effect on treatment efficacy in this retrospective analysis.

Right and Left Ventricular Outflow Tract Tachycardias: Evidence for a Common Electrophysiologic Mechanism

INTRODUCTION

"Idiopathic" ventricular arrhythmias most often arise from the right ventricular outflow tract (RVOT), although arrhythmias from the left ventricular outflow tract (LVOT) are also observed. While previous work has elucidated the mechanism and electropharmacologic profile of RVOT arrhythmias, it is unclear whether those from the LVOT share these properties. The purpose of this study was to characterize the electropharmacologic properties of RVOT and LVOT arrhythmias.

METHODS AND RESULTS

One hundred twenty-two consecutive patients (61 male; 50.9 +/- 15.2 years) with outflow tract arrhythmias comprise this series, 100 (82%) with an RVOT origin, and 22 (18%) with an LVOT origin. The index arrhythmia was similar: sustained ventricular tachycardia (VT) (RVOT = 28%, LVOT = 36%), nonsustained VT (RVOT = 40%, LVOT = 23%), and premature ventricular complexes (RVOT = 32%, LVOT = 41%) (P = 0.32). Cardiac magnetic resonance imaging and microvolt T-wave alternans results (normal/indeterminate) were also comparable. In addition, 41% with RVOT foci and 50% with LVOT foci were inducible for sustained VT (P = 0.48), and induction of VT was catecholamine dependent in a majority of patients in both groups (66% and 73%; RVOT and LVOT, respectively; P = 1.0). VT was sensitive to adenosine (88% and 78% in the RVOT and LVOT groups, respectively, P = 0.59) as well as blockade of the slow-inward calcium current (RVOT = 70%, LVOT = 80%; P = 1.00) in both groups.

CONCLUSIONS

Electrophysiologic and pharmacologic properties, including sensitivity to adenosine, are similar for RVOT and LVOT arrhythmias. Despite disparate sites of origin, these data suggest a common arrhythmogenic mechanism, consistent with cyclic AMP-mediated triggered activity. Based on these similarities, these arrhythmias should be considered as a single entity, and classified together as "outflow tract arrhythmias."

Inflation of Sensitivity of Cervical Cancer Screening Tests Secondary to Correlated Error in Colposcopy

OBJECTIVE

To determine whether the sensitivity of screening tests that miss small cervical intraepithelial neoplasia (CIN) 2 or worse (e.g., acetic acid-aided visual inspection) is inflated when the criterion standard (colposcopic-directed biopsy) misses the same small CIN 2 or worse.

MATERIALS AND METHODS

One thousand nine hundred twenty-eight women were screened using acetic acid-aided visual inspection, self-tests, and direct tests for high-risk human papillomavirus, and using liquid-based cytologic screening. All women underwent colposcopy with biopsy. If a cervical quadrant had no lesion, a random biopsy at the squamocolumnar junction within that quadrant was obtained. All patients underwent endocervical curettage (ECC). Differences in sensitivity for CIN 2 or worse of screening tests were compared with criterion standards of colposcopically directed biopsy and colposcopically directed biopsy, random biopsy, plus ECC.

RESULTS

Sixty-two of 83 women with CIN 2 or worse were diagnosed by colposcopically directed biopsy, 19 by random biopsy, and 2 solely by ECC. Fifty-six of the 83 women had CIN 2 or worse involving 0 to 2 quadrants (2 with 0 quadrants were diagnosed solely by positive ECC) and 27 of 83 had CIN 2 or worse results involving 3 to 4 quadrants. Colposcopically directed biopsy detected 35 of 56 women (62.5%) with CIN 2 or worse involving 0 to 2 cervical quadrants and 27 of 27 women (100%) with CIN 2 or worse involving 3 to 4 quadrants (p < .005). Acetic acid-aided visual inspection and cytologic analysis of high-grade squamous intraepithelial lesion or cancer detected 35 of 56 (62.5%) and 36 of 56 (64.3%) lesions involving 0 to 2 quadrants and 27 of 27 (100%) (p < .005) and 24 of 27 (88.9%; p < .05) lesions involving 3 to 4 quadrants. The sensitivity of direct human papillomavirus tests (97.6%) and cytologic analysis of atypical squamous cells of undetermined significance or worse (94.0%) for CIN 2 or worse were high and unaffected by lesion size. When the criterion standard was changed from colposcopically directed biopsy, random biopsy, plus ECC to colposcopically directed biopsy, the sensitivity of acetic acid-aided visual inspection and cytologic analysis of high-grade squamous intraepithelial lesion or worse for CIN 2 or worse increased from 75.9% to 85.5% (p > .1) and from 71.1% to 79.0% (p > .25). Sensitivities of other screening tests were unaffected by changing the criterion standard.

CONCLUSIONS

Criterion standards that miss the same CIN 2 or worse as the screening tests likely cause inflation of the sensitivity of those tests.

Skin toxicity associated with pegylated liposomal doxorubicin (40 mg/m2) in the treatment of gynecologic cancers

OBJECTIVES

To characterize the incidence of skin toxicity of pegylated liposomal doxorubicin (PLD) administered at a lower dose (40 mg/m(2)) in the treatment of advanced gynecologic malignancies.

METHODS

Medical charts of all patients who initiated PLD at a starting dose of 40 mg/m(2) from 1997 to 2003 for the treatment of gynecologic cancers were retrospectively reviewed. PLD was infused over 1-2 h and administered every 4-6 weeks. No patient had previously received doxorubicin. All patients were clinically assessed for adverse reactions including skin toxicity.

RESULTS

Ninety patients (mean age 62 years, range 45-82 years) were included in this analysis. There were 55 ovarian, 16 endometrial, 2 fallopian, and 17 primary peritoneal cancers. The median cumulative dose of PLD was 120 mg/m(2) (range 40-855 mg/m(2)) with a median of 3 cycles (range 1-25). 33/90 (37%) developed a skin reaction during therapy. The overall incidence of grade 1, 2, and 3 skin toxicity was 23 (26%), 9 (10%), and 1 (1%), respectively. Of the 23 cases of grade 1 toxicity, 16 (70%) occurred within 1-3 cycles. All 9 cases of grade 2 toxicity occurred within 1-3 cycles. The only case of grade 3 toxicity occurred after the first cycle. 28/30 (93%) patients who continued treatment did not experience further episodes of skin toxicity with subsequent cycles after a dose reduction (5-20 mg/m(2)). PLD was stopped in only 2/90 (2%) cases due to a skin reaction.

CONCLUSIONS

Severe skin toxicity (> or =grade 2) associated with PLD occurs infrequently when initial doses of 40 mg/m(2) are administered. When skin reactions appear, they usually occur early in the course of treatment, respond to dose reduction, and do not appear to limit the duration of treatment.

Association between factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T mutations and events of the arterial circulatory system: a meta-analysis of published studies

BACKGROUND

The association between the inherited gene mutations of factor V, prothrombin, and homocysteine metabolism and venous thromboembolic events is accepted widely; however, their influence on the arterial circulatory system remains controversial.

METHODS

We performed a MEDLINE search to identify published case-control and cohort studies correlating the factor V Leiden, prothrombin (PT) G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T (TT genotype) mutations with myocardial infarction, ischemic stroke, or peripheral vascular disease. Studies were included only when they adhered to specific diagnostic criteria for ischemic events and met the published methodological criteria. Odds ratios (ORs) with accompanying 95% CIs were calculated for each mutation and clinical end points with a random-effects model (DerSimonian and Laird method).

RESULTS

The association between inherited gene mutations and arterial ischemic events was modest: factor V Leiden mutation (OR, 1.21; 95% CI, 0.99-1.49), PT G20210A mutation (OR, 1.32; 95% CI, 1.03-1.69), and MTHFR TT mutation (OR, 1.20; 95% CI, 1.02-1.41). Subgroup analyses of younger patients (<55 years old) and of women revealed slightly stronger associations overall.

CONCLUSIONS

Genetic abnormalities specific to factor V, prothrombin,and homocysteine metabolism increase the risk for myocardial infarction and ischemic stroke, particularly among younger patients and women. Because the overall association is only modest, screening studies should be limited to carefully selected patient populations. The individual propensity for arterial and venous thrombosis is likely influenced by differing local mechanisms, systemic mechanisms, or both.

Limits of detection of regional differences in vasodilated flow in viable myocardium by first-pass magnetic resonance perfusion imaging

BACKGROUND

Perfusion imaging techniques intended to identify regional limitations in coronary flow reserve in viable myocardium need to identify 2-fold differences in regional flow during coronary vasodilation consistently. This study evaluated the suitability of current first-pass magnetic resonance approaches for evaluating such differences, which are 1 to 2 orders of magnitude less than in myocardial infarction.

METHODS AND RESULTS

Graded regional differences in vasodilated flow were produced in chronically instrumented dogs with either left circumflex (LCx) infusion of adenosine or partial LCx occlusion during global coronary vasodilation. First-pass myocardial signal intensity-time curves were obtained after right atrial injection of gadoteridol (0.025 mmol/kg) with an MRI inversion recovery true-FISP sequence. The area under the initial portion of the LCx curve was compared with that of a curve from a remote area of the ventricle. Relative LCx and remote flows were assessed simultaneously with microspheres. The ratio of LCx and remote MRI curve areas and the ratio of LCx and remote microsphere concentrations were highly correlated and linearly related over a 5-fold range of flow differences (y=0.96 x+/-0.07, P<0.0001, r(2)=0.87). The 95% confidence limits for individual MRI measurements were +/-35%. Regional differences of >/=2-fold were consistently apparent in unprocessed MR images.

CONCLUSIONS

Clinically relevant regional reductions in vasodilated flow in viable myocardium can be detected with 95% confidence over the range of 1 to 5 times resting flow. This suggests that MRI can identify and quantify limitations in perfusion reserve that are expected to be produced by stenoses of >/=70%.

Erythrocyte membrane ATP binding cassette (ABC) proteins: MRP1 and CFTR as well as CD39 (ecto-apyrase) involved in RBC ATP transport and elevated blood plasma ATP of cystic fibrosis

In addition to the better-known roles of the erythrocyte in the transport of oxygen and carbon dioxide, the concept that the red blood cell is involved in the transport and release of ATP has been evolving (J. Luthje, Blut 59, 367, 1989; G. R. Bergfeld and T. Forrester, Cardiovasc. Res. 26, 40, 1992; M. L. Ellsworth et al., Am. J. Physiol. 269, H2155, 1995; R. S. Sprague et al., Am. J. Physiol. 275, H1726, 1998). Membrane proteins involved in the release of ATP from erythrocytes now appear to include members of the ATP binding cassette (ABC) family (C. F. Higgins, Annu. Rev. Cell Biol. 8, 67, 1992; C. F. Higgins, Cell 82, 693, 1995). In addition to defining physiologically the presence of ABC proteins in RBCs, accumulating gel electrophoretic evidence suggests that the cystic fibrosis transmembrane conductance regulator (CFTR) and the multidrug resistance-associated protein (MRP1), respectively, constitute significant proteins in the red blood cell membrane. As such, this finding makes the mature erythrocyte compartment a major mammalian repository of these important ABC proteins. Because of its relative structural simplicity and ready accessibility, the erythrocyte offers an ideal system to explore details of the physiological functions of ABC proteins. Moreover, the presence of different ABC proteins in a single membrane implies that interaction among these proteins and with other membrane proteins may be the norm and not the exception in terms of modulation of their functions.

Transmural extent of acute myocardial infarction predicts long-term improvement in contractile function

BACKGROUND

Previous animal studies have demonstrated that the transmural extent of acute myocardial infarction defined by contrast-enhanced MRI (ceMRI) relates to early restoration of flow and future improvements in contractile function. We tested the hypothesis that ceMRI would have similar predictive value in humans.

METHODS AND RESULTS

Twenty-four patients who presented with their first myocardial infarction and were successfully revascularized underwent cine and ceMRI of their heart within 7 days (scan 1) of the peak MB band of creatine kinase. Cine MRI was repeated 8 to 12 weeks later (scan 2). The transmural extent of infarction on scan 1 and wall thickening on both scans were determined using a 72-segment model. A total of 524 of 1571 segments (33%) were dysfunctional on scan 1. Improvement in segmental contractile function on scan 2 was inversely related to the transmural extent of infarction on scan 1 (P=0.001). Improvement in global contractile function, as assessed by ejection fraction and mean wall thickening score, was not predicted by peak creatine kinase-MB (P=0.66) or by total infarct size, as defined by MRI (P=0.70). The best predictor of global improvement was the extent of dysfunctional myocardium that was not infarcted or had infarction comprising <25% of left ventricular wall thickness (P<0.005 for ejection fraction, P<0.001 for mean wall thickening score).

CONCLUSION

In patients with acute myocardial infarction, the transmural extent of infarction defined by ceMRI predicts improvement in contractile function.

Theory of high-speed MR imaging of the human heart with the selective line acquisition mode

Selective line acquisition mode (SLAM) reduces magnetic resonance imaging time by a factor n relative to conventional techniques. Seventeen patients with cardiac disease and three volunteers were examined with SLAM and two-frame interpolation (2FI). SLAM images were sharper than 2FI images and showed well-defined endocardial borders. SLAM is best suited for fast imaging of moving objects, such as the heart, confined to 1/n of the field of view.

Visualization of discrete microinfarction after percutaneous coronary intervention associated with mild creatine kinase-MB elevation

BACKGROUND

Mild elevations in creatine kinase-MB (CK-MB) are common after successful percutaneous coronary interventions and are associated with future adverse cardiac events. The mechanism for CK-MB release remains unclear. A new contrast-enhanced MRI technique allows direct visualization of myonecrosis.

METHODS AND RESULTS

Fourteen patients without prior infarction underwent cine and contrast-enhanced MRI after successful coronary stenting; 9 patients had procedure-related CK-MB elevation, and 5 did not (negative controls). The mean age of all patients was 61 years, 36% had diabetes, 43% had multivessel coronary artery disease, and all had a normal ejection fraction. Twelve patients (86%) received an intravenous glycoprotein IIb/IIIa inhibitor; none underwent atherectomy, and all had final TIMI 3 flow. Of the 9 patients with CK-MB elevation, 5 had a minor side branch occlusion during stenting, 2 had transient ECG changes, and none developed Q-waves. The median CK-MB was 21 ng/mL (range, 12 to 93 ng/mL), which is 2.3x the upper limit of normal. Contrast-enhanced MRI demonstrated discrete regions of hyperenhancement within the target vessel perfusion territory in all 9 patients. Only one developed a new wall motion abnormality. The median estimated mass of myonecrosis was 2.0 g (range, 0.7 to 12.2 g), or 1.5% of left ventricular mass (range, 0.4% to 6.0%). Hyperenhancement persisted in 5 of the 6 who underwent a repeat MRI at 3 to 12 months. No control patient had hyperenhancement.

CONCLUSIONS

Contrast-enhanced MRI provides an anatomical correlate to biochemical evidence of procedure-related myocardial injury, despite the lack of ECG changes or wall motion abnormalities. Mild elevation of CK-MB after percutaneous coronary intervention is the result of discrete microinfarction.

An improved MR imaging technique for the visualization of myocardial infarction

PURPOSE

To design a segmented inversion-recovery turbo fast low-angle shot (turboFLASH) magnetic resonance (MR) imaging pulse sequence for the visualization of myocardial infarction, compare this technique with other MR imaging approaches in a canine model of ischemic injury, and evaluate its utility in patients with coronary artery disease.

MATERIALS AND METHODS

Six dogs and 18 patients were examined. In dogs, infarction was produced and images were acquired by using 10 different pulse sequences. In patients, the segmented turboFLASH technique was used to acquire contrast material-enhanced images 19 days +/- 7 (SD) after myocardial infarction.

RESULTS

Myocardial regions of increased signal intensity were observed in all animals and patients at imaging. With the postcontrast segmented turboFLASH sequence, the signal intensity of the infarcted myocardium was 1,080% +/- 214 higher than that of the normal myocardium in dogs-nearly twice that of the next best sequence tested and approximately 10-fold greater than that in previous reports. All 18 patients with myocardial infarction demonstrated high signal intensity at imaging. On average, the signal intensity of the high-signal-intensity regions in patients was 485% +/- 43 higher than that of the normal myocardium.

CONCLUSION

The segmented inversion-recovery turboFLASH sequence produced the greatest differences in regional myocardial signal intensity in animals. Application of this technique in patients with infarction substantially improved differentiation between injured and normal regions.

Visualisation of presence, location, and transmural extent of healed Q-wave and non-Q-wave myocardial infarction

BACKGROUND

A technical advance in contrast-enhanced magnetic resonance imaging (MRI) has significantly improved image quality. We investigated whether healed myocardial infarction can be visualised as hyperenhanced regions with this new technique, and whether assessment of the transmural extent of infarction yields new physiological data.

METHODS

82 MRI examinations were carried out in three groups: patients with healed myocardial infarction; patients with non-ischaemic cardiomyopathy; and healthy volunteers. Patients with healed myocardial infarction were prospectively enrolled after enyzmatically proven necrosis and imaged 3 months (SD 1) or 14 months (7) later. The MRI procedure used a segmented inversion-recovery gradient-echo sequence after gadolinium administration. Findings were compared with those of coronary angiography, electrocardiography, cine MRI, and creatine kinase measurements.

FINDINGS

29 (91%) of 32 patients with infarcts imaged at 3 months (13 non-Q-wave) and all of 19 imaged at 14 months (eight non-Q-wave) showed hyperenhancement. In patients in whom the infarct-related-artery was identified by angiography, 24 of 25 imaged at 3 months and all of 14 imaged at 14 months had hyperenhancement in the appropriate territory. None of the 20 patients with non-ischaemic cardiomyopathy or the 11 healthy volunteers showed hyperenhancement. Irrespective of the presence or absence of Q waves, the majority of patients with hyperenhancement had only non-transmural involvement. Normal left-ventricular contraction was shown in seven patients examined at 3 months and three examined at 14 months, but in these cases hyperenhancement was limited to the subendocardium.

INTERPRETATION

The presence, location, and transmural extent of healed Q-wave and non-Q-wave myocardial infarction can be accurately determined by contrast-enhanced MRI.

An improved MR imaging technique for the visualization of myocardial infarction

PURPOSE

To design a segmented inversion-recovery turbo fast low-angle shot (turboFLASH) magnetic resonance (MR) imaging pulse sequence for the visualization of myocardial infarction, compare this technique with other MR imaging approaches in a canine model of ischemic injury, and evaluate its utility in patients with coronary artery disease.

MATERIALS AND METHODS

Six dogs and 18 patients were examined. In dogs, infarction was produced and images were acquired by using 10 different pulse sequences. In patients, the segmented turboFLASH technique was used to acquire contrast material-enhanced images 19 days +/- 7 (SD) after myocardial infarction.

RESULTS

Myocardial regions of increased signal intensity were observed in all animals and patients at imaging. With the postcontrast segmented turboFLASH sequence, the signal intensity of the infarcted myocardium was 1,080% +/- 214 higher than that of the normal myocardium in dogs-nearly twice that of the next best sequence tested and approximately 10-fold greater than that in previous reports. All 18 patients with myocardial infarction demonstrated high signal intensity at imaging. On average, the signal intensity of the high-signal-intensity regions in patients was 485% +/- 43 higher than that of the normal myocardium.

CONCLUSION

The segmented inversion-recovery turboFLASH sequence produced the greatest differences in regional myocardial signal intensity in animals. Application of this technique in patients with infarction substantially improved differentiation between injured and normal regions.

The use of contrast-enhanced magnetic resonance imaging to identify reversible myocardial dysfunction

BACKGROUND

Recent studies indicate that magnetic resonance imaging (MRI) after the administration of contrast material can be used to distinguish between reversible and irreversible myocardial ischemic injury regardless of the extent of wall motion or the age of the infarct. We hypothesized that the results of contrast-enhanced MRI can be used to predict whether regions of abnormal ventricular contraction will improve after revascularization in patients with coronary artery disease.

METHODS

Gadolinium-enhanced MRI was performed in 50 patients with ventricular dysfunction before they underwent surgical or percutaneous revascularization. The transmural extent of hyperenhanced regions was postulated to represent the transmural extent of nonviable myocardium. The extent of regional contractility at the same locations was determined by cine MRI before and after revascularization in 41 patients.

RESULTS

Contrast-enhanced MRI showed hyperenhancement of myocardial tissue in 40 of 50 patients before revascularization. In all patients with hyperenhancement the difference in image intensity between hyperenhanced regions and regions without hyperenhancement was more than 6 SD. Before revascularization, 804 of the 2093 myocardial segments analyzed (38 percent) had abnormal contractility, and 694 segments (33 percent) had some areas of hyperenhancement. In an analysis of all 804 dysfunctional segments, the likelihood of improvement in regional contractility after revascularization decreased progressively as the transmural extent of hyperenhancement before revascularization increased (P<0.001). For instance, contractility increased in 256 of 329 segments (78 percent) with no hyperenhancement before revascularization, but in only 1 of 58 segments with hyperenhancement of more than 75 percent of tissue. The percentage of the left ventricle that was both dysfunctional and not hyperenhanced before revascularization was strongly related to the degree of improvement in the global mean wall-motion score (P<0.001) and the ejection fraction (P<0.001) after revascularization.

CONCLUSIONS

Reversible myocardial dysfunction can be identified by contrast-enhanced MRI before coronary revascularization.

Contrast-enhanced magnetic resonance imaging of myocardium at risk: distinction between reversible and irreversible injury throughout infarct healing

OBJECTIVES

We sought to determine the relationship of delayed hyperenhancement by contrast magnetic resonance imaging (MRI) to viable and nonviable myocardium within the region at risk throughout infarct healing.

BACKGROUND

The relationship of delayed MRI contrast enhancement patterns to injured but viable myocardium within the ischemic bed at risk has not been established.

METHODS

We compared in vivo and ex vivo MRI contrast enhancement to histopathologic tissue sections encompassing the entire left ventricle in dogs (n = 24) subjected to infarction with (n = 12) and without (n = 12) reperfusion at 4 h, 1 day, 3 days, 10 days, 4 weeks and 8 weeks. In vivo MR imaging was performed 30 min after contrast injection.

RESULTS

The sizes and shapes of in vivo myocardial regions of elevated image intensity (828+/-132% of remote) were the same as those observed ex vivo (241 slices, r = 0.99, bias = 0.05+/-1.6% of left ventricle [LV]). Comparison of ex vivo MRI to triphenyltetrazolim chloride-stained sections demonstrated that the spatial extent of hyperenhancement was the same as the spatial extent ofinfarction at every stage of healing (510 slices, lowest r = 0.95, largest bias = 1.7+/-2.9% of LV). Conversely, hyperenhanced regions were smaller than the ischemic bed at risk defined by fluorescent microparticles at every stage of healing (239 slices, 35+/-24% of risk region, p<0.001). Image intensities of viable myocardium within the risk region were the same as those of remote, normal myocardium (102+/-9% of remote, p = NS).

CONCLUSIONS

Delayed contrast enhancement by MRI distinguishes between viable and nonviable regions within the myocardium at risk throughout infarct healing.

Microvascular integrity and the time course of myocardial sodium accumulation after acute infarction

Loss of membrane permeability caused by ischemia leads to cellular sodium accumulation and myocardial edema. This phenomenon has important implications to left ventricular structure and function in the first hours after myocardial infarction. We hypothesized that during this period of time, after prolonged coronary occlusion and complete reflow, the rate of myocardial sodium accumulation is governed by microvascular integrity. We used 3-dimensional (23)Na MRI to monitor myocardial sodium content changes over time in an in vivo closed-chest canine model (n=13) of myocardial infarction and reperfusion. Infarcts with microvascular obstruction (MO) defined by both radioactive microspheres and contrast-enhanced (1)H MRI showed a slower rate of sodium accumulation as well as lower blood flow at 20 minutes and 6 hours after reperfusion. Conversely, the absence of MO was associated with faster rates of sodium accumulation and greater blood flow restoration. In addition, infarct size by (23)Na MRI correlated best with infarct size by triphenyltetrazolium chloride and contrast-enhanced (1)H MRI at 9 hours after reperfusion. We conclude that in reperfused myocardial infarction, sodium accumulation is dependent on microvascular integrity and is slower in regions of MO compared with those with patent microvasculature. Finally, (23)Na MRI can be a useful tool for monitoring in vivo myocardial sodium content in acute myocardial infarction.

Early assessment of myocardial salvage by contrast-enhanced magnetic resonance imaging

BACKGROUND

Myocardial salvage after acute myocardial infarction is defined clinically by early restoration of flow and long-term improvement in contractile function. We hypothesized that contrast-enhanced magnetic resonance imaging (MRI), performed early after myocardial infarction, indexes myocardial salvage. We studied the relationship between the transmural extent of hyperenhancement by contrast-enhanced MRI, restoration of flow, and recovery of function.

METHODS AND RESULTS

The left anterior descending coronary artery was occluded in dogs (n=15) for either 45 minutes, 90 minutes, or permanently. Cine and contrast-enhanced MRI were performed 3 days after the procedure; cine MRI was also done 10 and 28 days after the procedure. The transmural extent of hyperenhancement and wall thickening were determined using a 60-segment model. The mean transmural extent of hyperenhancement for the 45-minute occlusion group was 22% of the 90-minute group and 18% of the permanent occlusion group (P:<0.05 for both). The transmural extent of hyperenhancement on day 3 was related to future improvement in both wall thickening score and absolute wall thickening at 10 and 28 days (P:<0.0001 for each). For example, of the 415 segments on day 3 that were dysfunctional and had <25% transmural hyperenhancement, 362 (87%) improved by day 28. Conversely, no segments (0 of 9) with 100% hyperenhancement improved. The transmural extent of hyperenhancement on day 3 was a better predictor of improvement in contractile function than occlusion time (P:<0.0001).

CONCLUSIONS

A reduction in the transmural extent of hyperenhancement by contrast-enhanced MRI early after myocardial infarction is associated with an early restoration of flow and future improvement in contractile function.

Evaluation of myocardial viability by MRI

Distinguishing between viable and non-viable myocardium is an important clinical issue. Several magnetic resonance (MR) techniques to address this issue have been proposed. Spectroscopy of phosphorus-31 and hydrogen-1 from creatine as well as imaging of sodium-23 and potassium-39 reflect information related to cellular metabolism. The spatial and temporal resolutions of these techniques are limited, however, by the small magnitude of the MR signal. Proton imaging techniques include examination of pathologic alterations in MR relaxation times (T1 and T2), wall thickness and thickening, cine MRI combined with low-dose dobutamine, first-pass contrast enhancement patterns, and delayed contrast enhancement patterns. Of the proton imaging approaches, cine MRI combined with low-dose dobutamine is supported by the largest body of clinical evidence supporting the hypothesis that the technique yields useful information regarding myocardial viability. Recent data suggest that delayed contrast enhancement examines the transmural extent of viable myocardium irrespective of contractile function and that this technique should also be considered in a clinical setting.

Relationship of MRI delayed contrast enhancement to irreversible injury, infarct age, and contractile function

BACKGROUND

Contrast MRI enhancement patterns in several pathophysiologies resulting from ischemic myocardial injury are controversial or have not been investigated. We compared contrast enhancement in acute infarction (AI), after severe but reversible ischemic injury (RII), and in chronic infarction.

METHODS AND RESULTS

In dogs, a large coronary artery was occluded to study AI and/or chronic infarction (n = 18), and a second coronary artery was chronically instrumented with a reversible hydraulic occluder and Doppler flowmeter to study RII (n = 8). At 3 days after surgery, cine MRI revealed reduced wall thickening in AI (5+/-6% versus 33+/-6% in normal, P<0.001). In RII, wall thickening before, during, and after inflation of the occluder for 15 minutes was 35+/-5%, 1+/-8%, and 21+/-10% and Doppler flow was 19.8+/-5.3, 0.2+/-0.5, and 56.3+/-17.7 (peak hyperemia) cm/s, respectively, confirming occlusion, transient ischemia, and reperfusion. Gd-DTPA-enhanced MR images acquired 30 minutes after contrast revealed hyperenhancement of AI (294+/-96% of normal, P<0.001) but not of RII (98+/-6% of normal, P = NS). Eight weeks later, the chronically infarcted region again hyperenhanced (253+/-54% of normal, n = 8, P<0.001). High-resolution (0.5 x 0.5 x 0.5 mm) ex vivo MRI demonstrated that the spatial extent of hyperenhancement was the same as the spatial extent of myocyte necrosis with and without reperfusion at 1 day (R = 0.99, P<0.001) and 3 days (R = 0.99, P<0.001) and collagenous scar at 8 weeks (R = 0.97, P<0.001).

CONCLUSIONS

In the pathophysiologies investigated, contrast MRI distinguishes between reversible and irreversible ischemic injury independent of wall motion and infarct age.

Relationship of elevated 23Na magnetic resonance image intensity to infarct size after acute reperfused myocardial infarction

BACKGROUND

Elevated 23Na MR image intensity after acute myocardial infarction has previously been shown to correspond to high tissue [Na+] and loss of myocardial viability. In this study, we explored the potential of in vivo 23Na MRI to assess infarct size and investigated possible mechanisms for elevated 23Na image intensity.

METHODS AND RESULTS

Thirteen dogs and 8 rabbits underwent in situ coronary artery occlusion and reperfusion and were imaged by 23Na MRI. For anatomically matched left ventricular short-axis cross sections (n=46), infarct size measured by in vivo 23Na MRI correlated well with triphenyltetrazolium chloride staining (r=0.87, y=0.92x+3.37, P<0.001). Elevated 23Na image intensity was observed in infarcted myocardium (206+/-37% of remote in dogs, P<0.001; 215+/-58% in rabbits, P<0.002) but was not observed after severe but reversible ischemic injury (101+/-11% of baseline, P=NS). High-resolution ex vivo imaging revealed that regions of elevated 23Na image intensity appeared to be identical to those of infarcted regions (r=0.97, y=0.92x+1.52, P<0.001). In infarcted regions, total tissue [Na+] was elevated (89+/-12 versus 37+/-9 mmol/L in control tissue, 156+/-60% increase, P<0.001) and was associated with increased intracellular sodium (254+/-68% of control, P<0.005) and an increased intracellular sodium/potassium ratio (868+/-512% of control, P<0.002). Morphometric analysis demonstrated only a minor increase in extracellular volume (17+/-8% versus 14+/-5%, P<0.05) in the infarcted territory.

CONCLUSIONS

Elevated 23Na MR image intensity in vivo measures infarct size after reperfused infarction in both a large and a small animal model. The mechanism of elevated 23Na image intensity is probably intracellular sodium accumulation secondary to loss of myocyte ionic homeostasis.