Myocardial Strain for the Differentiation of Myocardial Involvement in the Post-Acute Sequelae of COVID-19-A Multiparametric Cardiac MRI Study.

Myocardial involvement was shown to be associated with an unfavorable prognosis in patients with COVID-19, which could lead to fatal outcomes as in myocardial injury-induced arrhythmias and sudden cardiac death. We hypothesized that magnetic resonance imaging (MRI) myocardial strain parameters are sensitive markers for identifying subclinical cardiac dysfunction associated with myocardial involvement in the post-acute sequelae of COVID-19 (PASC). This study evaluated 115 subjects, including 65 consecutive COVID-19 patients, using MRI for the assessment of either post-COVID-19 myocarditis or other cardiomyopathies. Subjects were categorized, based on the results of the MRI exams, as having either 'suspected' or 'excluded' myocarditis. A control group of 50 matched individuals was studied. Along with parameters of global cardiac function, the MRI images were analyzed for measurements of the myocardial T1, T2, extracellular volume (ECV), strain, and strain rate. Based on the MRI late gadolinium enhancement and T1/T2/ECV mappings, myocarditis was suspected in 7 out of 22 patients referred due to concern of myocarditis and in 9 out of 43 patients referred due to concern of cardiomyopathies. The myocardial global longitudinal, circumferential, and radial strains and strain rates in the suspected myocarditis group were significantly smaller than those in the excluded myocarditis group, which in turn were significantly smaller than those in the control group. The results showed significant correlations between the strain, strain rate, and global cardiac function parameters. In conclusion, this study emphasizes the value of multiparametric MRI for differentiating patients with myocardial involvement in the PASC based on changes in the myocardial contractility pattern and tissue structure.

Development of a comprehensive cardiac atlas on a 1.5 Tesla Magnetic Resonance Linear Accelerator.

Background and purpose: The 1.5 Tesla (T) Magnetic Resonance Linear Accelerator (MRL) provides an innovative modality for improved cardiac imaging when planning radiation treatment. No MRL based cardiac atlases currently exist, thus, we sought to comprehensively characterize cardiac substructures, including the conduction system, from cardiac images acquired using a 1.5 T MRL and provide contouring guidelines. Materials and methods: Five volunteers were enrolled in a prospective protocol (NCT03500081) and were imaged on the 1.5 T MRL with Half Fourier Single-Shot Turbo Spin-Echo (HASTE) and 3D Balanced Steady-State Free Precession (bSSFP) sequences in axial, short axis, and vertical long axis. Cardiac anatomy was contoured by (AS) and confirmed by a board certified cardiologist (JR) with expertise in cardiac MR imaging. Results: A total of five volunteers had images acquired with the HASTE sequence, with 21 contours created on each image. One of these volunteers had additional images obtained with 3D bSSFP sequences in the axial plane and additional images obtained with HASTE sequences in the key cardiac planes. Contouring guidelines were created and outlined. 15-16 contours were made for the short axis and vertical long axis. The cardiac conduction system was demonstrated with eleven representative contours. There was reasonable variation of contour volume across volunteers, with structures more clearly delineated on the 3D bSSFP sequence. Conclusions: We present a comprehensive cardiac atlas using novel images acquired prospectively on a 1.5 T MRL. This cardiac atlas provides a novel resource for radiation oncologists in delineating cardiac structures for treatment with radiotherapy, with special focus on the cardiac conduction system.

Profibrotic COVID-19 subphenotype exhibits enhanced localized ER-dependent HSP47+ expression in cardiac myofibroblasts in situ.

We recently described a subgroup of autopsied COVID-19 subjects (∼40%), termed 'profibrotic phenotype,' who exhibited clusters of myofibroblasts (Mfbs), which were positive for the collagen-specific chaperone heat shock protein 47 (HSP47+) in situ. This report identifies increased, localized (hot spot restricted) expression of αSMA, COLα1, POSTN and FAP supporting the identity of HSP47+ cells as myofibroblasts and characterizing a profibrotic extracellular matrix (ECM) phenotype. Coupled with increased GRP78 in COVID-19 subjects, these data could reflect induction of the unfolded protein response for mitigation of proteostasis (i.e., protein homeostasis) dysfunction in discrete clusters of cells. ECM shifts in selected COVID-19 subjects occur without significant increases in either global trichrome positive staining or myocardial injury based quantitively on standard H&E scoring. Our findings also suggest distinct mechanism(s) for ECM remodeling in the setting of SARS-CoV-2 infection. The ratio of CD163+/CD68+ cells is increased in hot spots of profibrotic hearts compared with either controls or outside of hot spots in COVID-19 subjects. In sum, matrix remodeling of human COVID-19 hearts in situ is characterized by site-restricted profibrotic mediated (e.g., HSP47+ Mfbs, CD163+ Mφs) modifications in ECM (i.e., COLα1, POSTN, FAP), with a strong correlation between COLα1 and HSP47+cells within hot spots. Given the established associations of viral infection (e.g., human immunodeficiency virus; HIV), myocardial fibrosis and sudden cardiac death, early screening tools (e.g., plasma biomarkers, noninvasive cardiac magnetic resonance imaging) for diagnosis, monitoring and treatment of fibrotic ECM remodeling are warranted for COVID-19 high-risk populations.

Collagen-Specific HSP47+ Myofibroblasts and CD163+ Macrophages Identify Profibrotic Phenotypes in Deceased Hearts With SARS-CoV-2 Infections.

Background Cardiac fibrosis complicates SARS-CoV-2 infections and has been linked to arrhythmic complications in survivors. Accordingly, we sought evidence of increased HSP47 (heat shock protein 47), a stress-inducible chaperone protein that regulates biosynthesis and secretion of procollagen in heart tissue, with the goal of elucidating molecular mechanisms underlying cardiac fibrosis in subjects with this viral infection. Methods and Results Using human autopsy tissue, immunofluorescence, and immunohistochemistry, we quantified Hsp47+ cells and collagen α 1(l) in hearts from people with SARS-CoV-2 infections. Because macrophages are also linked to inflammation, we measured CD163+ cells in the same tissues. We observed irregular groups of spindle-shaped HSP47+ and CD163+ cells as well as increased collagen α 1(I) deposition, each proximate to one another in "hot spots" of ≈40% of hearts after SARS-CoV-2 infection (HSP47+ P<0.05 versus nonfibrotics and P<0.001 versus controls). Because HSP47+ cells are consistent with myofibroblasts, subjects with hot spots are termed "profibrotic." The remaining 60% of subjects dying with COVID-19 without hot spots are referred to as "nonfibrotic." No control subject exhibited hot spots. Conclusions Colocalization of myofibroblasts, M2(CD163+) macrophages, and collagen α 1(l) may be the first evidence of a COVID-19-related "profibrotic phenotype" in human hearts in situ. The potential public health and diagnostic implications of these observations require follow-up to further define mechanisms of viral-mediated cardiac fibrosis.

Onset of the COVID-19 pandemic reduced active time in patients with implanted cardiac devices.

BACKGROUND: Physical inactivity and sedentary behavior are modifiable risk factors for chronic disease and all-cause mortality that may have been negatively impacted by the COVID-19 shutdowns. METHODS: Accelerometry data was retrospectively collected from 332 permanent pacemaker (PPM) and 244 implantable cardiac defibrillation (ICD) patients for 6 time points: March 15-May 15, 2020 (pandemic period), January 1-March 14, 2020, October 1-December 31, 2019, March 15-May 15, 2019, January 1-March 14, 2019, and October 1-December 31, 2018. Paired t-tests, with Bonferroni correction, were used to compare time periods. RESULTS: Activity significantly decreased during the pandemic period compared to one year prior by an average of 0.53 ± 1.18h/day (P < 0.001) for PPM patients and 0.51 ± 1.2h/day (P < 0.001) for ICD patients. Stratification of subjects by active time (< 2 versus ≥ 2h/day) showed patients with < 2h, particularly those with ICDs, had modestly greater activity reductions with the pandemic onset. Logistical regression analyses suggest a trend toward a greater reduction in active time at the onset of the pandemic and an increased risk of hospital or emergency department (ED) admission for PPM patients, but not ICD patients. CONCLUSION: The onset of the pandemic in the United States was associated with a significant drop in PPM and ICD patient active hours that was modestly more pronounced in less active patients and cannot be explained by one year of aging or seasonal variation. If sustained, these populations may experience excess cardiovascular morbidity.

Value CMR: Towards a Comprehensive, Rapid, Cost-Effective Cardiovascular Magnetic Resonance Imaging.

Cardiac magnetic resonance imaging (CMR) is considered the gold standard for measuring cardiac function. Further, in a single CMR exam, information about cardiac structure, tissue composition, and blood flow could be obtained. Nevertheless, CMR is underutilized due to long scanning times, the need for multiple breath-holds, use of a contrast agent, and relatively high cost. In this work, we propose a rapid, comprehensive, contrast-free CMR exam that does not require repeated breath-holds, based on recent developments in imaging sequences. Time-consuming conventional sequences have been replaced by advanced sequences in the proposed CMR exam. Specifically, conventional 2D cine and phase-contrast (PC) sequences have been replaced by optimized 3D-cine and 4D-flow sequences, respectively. Furthermore, conventional myocardial tagging has been replaced by fast strain-encoding (SENC) imaging. Finally, T1 and T2 mapping sequences are included in the proposed exam, which allows for myocardial tissue characterization. The proposed rapid exam has been tested in vivo. The proposed exam reduced the scan time from >1 hour with conventional sequences to <20 minutes. Corresponding cardiovascular measurements from the proposed rapid CMR exam showed good agreement with those from conventional sequences and showed that they can differentiate between healthy volunteers and patients. Compared to 2D cine imaging that requires 12-16 separate breath-holds, the implemented 3D-cine sequence allows for whole heart coverage in 1-2 breath-holds. The 4D-flow sequence allows for whole-chest coverage in less than 10 minutes. Finally, SENC imaging reduces scan time to only one slice per heartbeat. In conclusion, the proposed rapid, contrast-free, and comprehensive cardiovascular exam does not require repeated breath-holds or to be supervised by a cardiac imager. These improvements make it tolerable by patients and would help improve cost effectiveness of CMR and increase its adoption in clinical practice.

Cardiac Magnetic Resonance for Early Detection of Radiation Therapy-Induced Cardiotoxicity in a Small Animal Model.

BACKGROUND: Over half of all cancer patients receive radiation therapy (RT). However, radiation exposure to the heart can cause cardiotoxicity. Nevertheless, there is a paucity of data on RT-induced cardiac damage, with limited understanding of safe regional RT doses, early detection, prevention and management. A common initial feature of cardiotoxicity is asymptomatic dysfunction, which if left untreated may progress to heart failure. The current paradigm for cardiotoxicity detection and management relies primarily upon assessment of ejection fraction (EF). However, cardiac injury can occur without a clear change in EF. OBJECTIVES: To identify magnetic resonance imaging (MRI) markers of early RT-induced cardiac dysfunction. METHODS: We investigated the effect of RT on global and regional cardiac function and myocardial T1/T2 values at two timepoints post-RT using cardiac MRI in a rat model of localized cardiac RT. Rats who received image-guided whole-heart radiation of 24Gy were compared to sham-treated rats. RESULTS: The rats maintained normal global cardiac function post-RT. However, a deterioration in strain was particularly notable at 10-weeks post RT, and changes in circumferential strain were larger than changes in radial or longitudinal strain. Compared to sham, circumferential strain changes occurred at the basal, mid-ventricular and apical levels (p<0.05 for all at both 8-weeks and 10-weeks post-RT), most of the radial strain changes occurred at the mid-ventricular (p=0.044 at 8-weeks post-RT) and basal (p=0.018 at 10-weeks post-RT) levels, and most of the longitudinal strain changes occurred at the apical (p=0.002 at 8-weeks post-RT) and basal (p=0.035 at 10-weeks post-RT) levels. Regionally, lateral myocardial segments showed the greatest worsening in strain measurements, and histologic changes supported these findings. Despite worsened myocardial strain post-RT, myocardial tissue displacement measures were maintained, or even increased. T1/T2 measurements showed small non-significant changes post-RT compared to values in non-irradiated rats. CONCLUSIONS: Our findings suggest MRI regional myocardial strain is a sensitive imaging biomarker for detecting RT-induced subclinical cardiac dysfunction prior to compromise of global cardiac function.

Pandemic Perspective: Commonalities Between COVID-19 and Cardio-Oncology.

Overlapping commonalities between coronavirus disease of 2019 (COVID-19) and cardio-oncology regarding cardiovascular toxicities (CVT), pathophysiology, and pharmacology are special topics emerging during the pandemic. In this perspective, we consider an array of CVT common to both COVID-19 and cardio-oncology, including cardiomyopathy, ischemia, conduction abnormalities, myopericarditis, and right ventricular (RV) failure. We also emphasize the higher risk of severe COVID-19 illness in patients with cardiovascular disease (CVD) or its risk factors or cancer. We explore commonalities in the underlying pathophysiology observed in COVID-19 and cardio-oncology, including inflammation, cytokine release, the renin-angiotensin-aldosterone-system, coagulopathy, microthrombosis, and endothelial dysfunction. In addition, we examine common pharmacologic management strategies that have been elucidated for CVT from COVID-19 and various cancer therapies. The use of corticosteroids, as well as antibodies and inhibitors of various molecules mediating inflammation and cytokine release syndrome, are discussed. The impact of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) is also addressed, since these drugs are used in cardio-oncology and have received considerable attention during the COVID-19 pandemic, since the culprit virus enters human cells via the angiotensin converting enzyme 2 (ACE2) receptor. There are therefore several areas of overlap, similarity, and interaction in the toxicity, pathophysiology, and pharmacology profiles in COVID-19 and cardio-oncology syndromes. Learning more about either will likely provide some level of insight into both. We discuss each of these topics in this viewpoint, as well as what we foresee as evolving future directions to consider in cardio-oncology during the pandemic and beyond. Finally, we highlight commonalities in health disparities in COVID-19 and cardio-oncology and encourage continued development and implementation of innovative solutions to improve equity in health and healing.

A Pilot Study of Cardiac MRI in Breast Cancer Survivors After Cardiotoxic Chemotherapy and Three-Dimensional Conformal Radiotherapy.

PURPOSE/OBJECTIVES: Node-positive breast cancer patients often receive chemotherapy and regional nodal irradiation. The cardiotoxic effects of these treatments, however, may offset some of the survival benefit. Cardiac magnetic resonance (CMR) is an emerging modality to assess cardiac injury. This is a pilot trial assessing cardiac damage using CMR in patients who received anthracycline-based chemotherapy and three-dimensional conformal radiotherapy (3DCRT) regional nodal irradiation using heart constraints. MATERIALS AND METHODS: Node-positive breast cancer patients (2000-2008) treated with anthracycline-based chemotherapy and 3DCRT regional nodal irradiation (including the internal mammary chain nodes) with heart ventricular constraints (V25 < 10%) were invited to participate. Cardiac tissues were contoured and analyzed separately for whole heart (pericardium) and for combined ventricles and left atrium (myocardium). CMR obtained ventricular function/dimensions, late gadolinium enhancement (LGE), global longitudinal strain (GLS), and extracellular volume fraction (ECV) as measures of cardiac injury and/or early fibrosis. CMR parameters were correlated with dose-volume constraints using Spearman correlations. RESULTS: Fifteen left-sided and five right-sided patients underwent CMR. Median diagnosis age was 50 (32-77). No patients had baseline cardiac disease before regional nodal irradiation. Median time after 3DCRT was 8.3 years (5.2-14.4). Median left-sided mean heart dose (MHD) was 4.8 Gy (1.1-11.2) and V25 was 5.7% (0-12%). Median left ventricular ejection fraction (LVEF) was 63%. No abnormal LGE was observed. No correlations were seen between whole heart doses and LVEF, LV mass, GLS, or LV dimensions. Increasing ECV did not correlate with increased heart or ventricular doses. However, correlations between higher LV mass and ventricular mean dose, V10, and V25 were seen. CONCLUSION: At a median follow-up of 8.3 years, this cohort of node-positive breast cancer patients who received anthracycline-based chemotherapy and regional nodal irradiation had no clinically abnormal CMR findings. However, correlations between ventricular mean dose, V10, and V25 and LV mass were seen. Larger corroborating studies that include advanced techniques for measuring regional heart mechanics are warranted.

Optimized cardiac functional MRI of small-animal models of cancer radiation therapy.

Cardiac MRI of small animal models of cancer radiation therapy (RT) is a valuable tool for studying the effect of RT on the heart. However, standard cardiac MRI exams require long scanning times, which is challenging for sick animals that may not survive extended periods of imaging under anesthesia. The purpose of this study is to develop an optimized, fast MRI exam for comprehensive cardiac functional imaging of small-animal models of cancer RT. Ten adult female rats (2 non-irradiated and 8 irradiated) were scanned using the developed exam. Optimal imaging parameters were determined, which minimized scanning time while ensuring measurement accuracy and avoiding imaging artifacts. This optimized, fast MRI exam lasted for 30 min, which was tolerated by all animals. EF was normal in all imaged rats, although it was significantly increased in the irradiated rats, which also showed ventricular hypertrophy. However, myocardial strain was significantly reduced in the irradiated rats. In conclusion, a fast MRI exam has been developed for comprehensive cardiac functional imaging of rats in 30 min, with optimized imaging parameters to ensure accurate measurements and tolerance by irradiated rats. The generated strain measurements provide an early marker of regional cardiac dysfunction before global function is affected.

Tachyarrhythmia discriminator for implantable cardioverter-defibrillators in bundle branch block.

BACKGROUND: Inaccurate arrhythmia classification by implantable cardioverter-defibrillators (ICDs) contributes to inappropriate shocks and increased health care utilization. OBJECTIVE: The purpose of this study was to evaluate the ability of a novel discriminator using far-field (FF) and near-field (NF) right ventricular lead electrograms (EGMs) to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) in patients with underlying conducted narrow QRS, right bundle branch block (RBBB), and left bundle branch block (LBBB). METHODS: ICD interrogations were reviewed, identifying subjects with tachycardia events at least 5 beats in duration with stable morphology and cycle length. FF to NF (FF-NF) EGM intervals during tachycardia and baseline conducted rhythm were measured using digital calipers. Events with uncertain tachycardia rhythm mechanism were excluded. RESULTS: Ninety-five subjects were included. Mean FF-NF interval during tachycardia was significantly lower during SVT than VT (25.8 ± 12.0 ms vs 91.0 ± 37.2 ms; P <.001). Participants with LBBB (n = 22) and RBBB (n = 21) had significantly lower mean FF-NF intervals during SVT compared with VT (LBBB 25.6 ± 7.26 ms vs 93.1 ± 41.5 ms; P <.001; RBBB 30.0 ± 16.6 ms vs 101.7 ± 34.3 ms; P <.001). In this cohort, FF-NF interval cutoff of 100 ms was 100% specific for VT discrimination regardless of underlying QRS morphology, with sensitivity of 46%, 50%, and 38% for LBBB, RBBB, and narrow QRS, respectively. CONCLUSION: Prolonged FF-NF interval on intracardiac EGM during tachycardia is a highly specific discriminator for VT, regardless of baseline QRS morphology.

Assessing the Risks Associated with MRI in Patients with a Pacemaker or Defibrillator.

BACKGROUND: The presence of a cardiovascular implantable electronic device has long been a contraindication for the performance of magnetic resonance imaging (MRI). We established a prospective registry to determine the risks associated with MRI at a magnetic field strength of 1.5 tesla for patients who had a pacemaker or implantable cardioverter-defibrillator (ICD) that was "non-MRI-conditional" (i.e., not approved by the Food and Drug Administration for MRI scanning). METHODS: Patients in the registry were referred for clinically indicated nonthoracic MRI at a field strength of 1.5 tesla. Devices were interrogated before and after MRI with the use of a standardized protocol and were appropriately reprogrammed before the scanning. The primary end points were death, generator or lead failure, induced arrhythmia, loss of capture, or electrical reset during the scanning. The secondary end points were changes in device settings. RESULTS: MRI was performed in 1000 cases in which patients had a pacemaker and in 500 cases in which patients had an ICD. No deaths, lead failures, losses of capture, or ventricular arrhythmias occurred during MRI. One ICD generator could not be interrogated after MRI and required immediate replacement; the device had not been appropriately programmed per protocol before the MRI. We observed six cases of self-terminating atrial fibrillation or flutter and six cases of partial electrical reset. Changes in lead impedance, pacing threshold, battery voltage, and P-wave and R-wave amplitude exceeded prespecified thresholds in a small number of cases. Repeat MRI was not associated with an increase in adverse events. CONCLUSIONS: In this study, device or lead failure did not occur in any patient with a non-MRI-conditional pacemaker or ICD who underwent clinically indicated nonthoracic MRI at 1.5 tesla, was appropriately screened, and had the device reprogrammed in accordance with the prespecified protocol. (Funded by St. Jude Medical and others; MagnaSafe ClinicalTrials.gov number, NCT00907361 .).

The relationship between defibrillation threshold and total mortality.

BACKGROUND: The relationship between the defibrillation threshold (DFT) and total mortality is unclear. METHODS: A university hospital prospectively maintained implantable defibrillator (ICD) database identified 508 patients who underwent ICD implantation and had DFT testing performed at implant. Patients were placed in one of three groups based on the implant DFT (high (≥20 J), moderate (19-11 J), or low DFT (≤10 J)). RESULTS: Sixty-seven patients had a high DFT, 216 had a moderate DFT, and 225 had a low DFT. The mean left ventricular ejection fraction (LVEF) was 0.25, 0.28, and 0.30 in the high, moderate, and low DFT groups, respectively, (p = 0.04). There were significantly more patients with a subcutaneous electrode in the high DFT group (p < 0.001), more patients taking amiodarone (p < 0.001), and more patients on oral anticoagulation (p = 0.04). There were a total of 140 deaths during the follow-up period (mean 3.2 ± 1.7 years). There were 24 deaths in the high DFT group (35.8%), 62 in the moderate DFT group (28.7%), and 54 in the low DFT group (24.0%) (p = 0.05). Implant DFT was a significant predictor of mortality (p = 0.01), as was age, LVEF (p < 0.001), CAD (p = 0.01), amiodarone use (p = 0.02), and hematoma at implant (p = 0.01). An elevated DFT was an independent predictor of mortality after controlling for all significant univariate variables (p = 0.004). CONCLUSIONS: A high-implant DFT predicts an adverse prognosis, even when an adequate ICD safety margin is present.

Effectiveness of VF induction with DC fibber versus conventional induction methods in patients on chronic amiodarone therapy.

BACKGROUND: Amiodarone therapy, especially chronic, can result in difficult ventricular fibrillation (VF) inductions during implantable cardioverter defibrillator (ICD) testing. The efficacy of various VF induction methods on patients treated with amiodarone has not been well described. This prospective analysis evaluated the impact of direct current (DC) fibber, burst fibber, and synchronized T-wave shock VF induction methods. METHODS: Data were collected from one study and two enrolling centers totaling 14 ICD patients (92.9 % male, age 64.3 years (range 23.6-81.2)). A minimum of two successful VF inductions from each patient were required to be included in the study analysis. Each VF induction method was attempted in each patient. Non-sustained VF resulting in an aborted shock was considered an induction failure. All 14 patients were on chronic amiodarone therapy. RESULTS: From a total of 42 attempted inductions, 25 (59.5 %) were successful at inducing VF. The success rates of effective induction of VF during the first attempt using DC, burst, and Shock-on-T are 100, 50, and 28.6 %, respectively. DC fibber had significantly higher VF induction rates than Shock-on-T (p = 0.004) or burst fibber (p = 0.02). There was no difference between Shock-on-T and burst fibber (p = 0.45). CONCLUSION: The success rate of VF induction using DC fibber method is significantly higher than either Shock-on-T or burst fibber induction methods for patients on chronic amiodarone therapy. This may facilitate defibrillation threshold testing in such patients.

A comparison of cardiac magnetic resonance imaging peri-infarct border zone quantification strategies for the prediction of ventricular tachyarrhythmia inducibility.

BACKGROUND: Peri-infarct border zone (BZ) as quantified by late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (MRI) has been proposed as a risk stratification tool, and is associated with increased mortality. BZ has been measured by various methods in the literature. We assessed which BZ analysis best predicts inducible arrhythmia during electrophysiological study (EPS). METHODS: LGE was performed in 47 patients with coronary artery disease referred for EPS to assess for ventricular tachycardia (VT). LGE data was analyzed for BZ quantification by 3 previously published methods. Method I (BZ-I) used pixels 2-3 standard deviations over the mean of normal tissue, expressed as % of left ventricular mass, Method II (BZ-II, as described by Yan) and Method III (BZ-III, as described by Schmidt). EPS results were classified as negative (non-inducible) or positive (monomorphic VT - MVT). RESULTS: There were 47 subjects-age 61.7 years, 72% male. During EPS, 20 patients were non-inducible and 18 had induced MVT. Ejection fraction was not significantly different between non-inducible patients and those with MVT (34.1% vs. 28.5%, p = 0.13). BZ-I was significantly different (1.4% vs. 2.6%, p = 0.001), but not BZ-II (7.9% vs. 6.9%, p = 0.68) or BZ-III (2.7 g vs. 2.1 g, p = 0.88). Multivariate analysis demonstrated that only BZ-I was an independent predictor of EPS outcome after controling for infarct size (OR 1.97 per % change, 95% CI 1.04-3.73, p = 0.04). CONCLUSIONS: This study demonstrates significant variability between the published methods for measuring BZ. Also, BZ-I is a stronger predictor of inducible MVT during EPS than ejection fraction and infarct size. BZ may be another LGE marker of elevated risk of arrhythmia.

Atrial Fibrillation in Acute Coronary Syndrome.

Atrial fibrillation (AF) is a common cardiac arrhythmia occurring in an estimated 2.7 to 6.1 million people in the United States. The risk factors for the development of AF are very similar to those for developing coronary artery disease, and AF is often associated with acute coronary syndrome (ACS) and acute myocardial infarction (MI). Overall, AF complicates approximately 10% of acute infarcts and the incidence rate is comparable between the thrombolytic and percutaneous coronary intervention (PCI) eras. Prior to widespread use of thrombolysis, the incidence of AF during acute MI was as high as 18%. Moreover, AF is a marker for increased long term mortality post infarct. Over the past 20 years, the relative mortality risk for patients with AF post MI has remained around 2.5 times that for patients without AF. The treatment of AF in the setting of MI and ACS is similar to without; however there is often an increased urgency to limiting rapid heart rates which may exacerbate acute ischemia. Cardioversion and IV amiodarone may be utilized more liberally in this setting than otherwise. Anticoagulation is usually required both for the treatment of MI and possible PCI, as well as for cerebral vascular accident prevention from AF-induced thromboembolism. Often patients require triple-therapy for optimal treatment of both conditions, and special considerations for bleeding risk must be analyzed.