Andrew C.T. Ha

A Citywide Protocol for Primary PCI in ST-Segment Elevation Myocardial Infarction

BACKGROUND If primary percutaneous coronary intervention (PCI) is performed promptly, the procedure is superior to fibrinolysis in restoring flow to the infarct-related artery in patients with ST-segment elevation myocardial infarction. The benchmark for a timely PCI intervention has become a door-to-balloon time of less than 90 minutes. Whether regional strategies can be developed to achieve this goal is uncertain. METHODS We developed an integrated-metropolitan-area approach in which all patients with ST-segment elevation myocardial infarction were referred to a specialized center for primary PCI. We sought to determine whether there was a difference in door-to-balloon times between patients who were referred directly from the field by paramedics trained in the interpretation of electrocardiograms and patients who were referred by emergency department physicians. RESULTS Between May 1, 2005, and April 30, 2006, a total of 344 consecutive patients with ST-segment elevation myocardial infarction were referred for primary PCI: 135 directly from the field and 209 from emergency departments. Primary PCI was performed in 93.6% of patients. The median door-to-balloon time was shorter in patients referred from the field (69 minutes; interquartile range, 43 to 87) than in patients needing interhospital transfer (123 minutes; interquartile range, 101 to 153; P<0.001). Door-to-balloon times of less than 90 minutes were achieved in 79.7% of patients who were transferred from the field and in 11.9% of those transferred from emergency departments (P<0.001). CONCLUSIONS Guideline door-to-balloon-times were more often achieved when trained paramedics independently triaged and transported patients directly to a designated primary PCI center than when patients were referred from emergency departments.

Impact of QRS Morphology and Duration on Outcomes After Cardiac Resynchronization Therapy Results From the Resynchronization–Defibrillation for Ambulatory Heart Failure Trial (RAFT)

Background—The impact of QRS morphology and duration on the effectiveness of cardiac resynchronization therapy (CRT) has been usually assessed separately. The interaction between these 2 simple ECG parameters and their effect on CRT has not been systematically assessed in a large-scale clinical trial. Methods and Results—The Resynchronization–Defibrillation for Ambulatory Heart Failure Trial showed that implantable cardioverter defibrillator-CRT was associated with a significant reduction in the primary end point of all-cause mortality or heart failure hospitalization. For this substudy, we excluded patients in atrial fibrillation and those with a previous pacemaker. All baseline ECGs were reviewed by a panel of 3 experienced electrocardiographers. A total of 1483 patients were included in this study. Of these, 1175 had left bundle-branch block (LBBB) and 308 had non-LBBB. In patients with LBBB receiving implantable cardioverter defibrillator-CRT, there was a reduction in the primary outcome and in each individual component of the primary outcome. Furthermore, there was continuous relationship between QRS duration and extent of benefit. In patients with non-LBBB and QRS ≥160 ms, the hazard ratio for the primary outcome was 0.52 (0.29–0.96; P=0.033); in patients with QRS <160 ms, the hazard ratio was 1.38 (0.88–2.14; P=0.155). Conclusions—In patients with LBBB, there was a continuous relationship between broader QRS and greater benefit from implantable cardioverter defibrillator-CRT. However, our data do not support the use of implantable cardioverter defibrillator-CRT in patients with non-LBBB, especially when the QRS duration is <160 ms. There may be some delayed benefit when the QRS is ≥160 ms, but this needs further investigation. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00251251.Background— The impact of QRS morphology and duration on the effectiveness of cardiac resynchronization therapy (CRT) has been usually assessed separately. The interaction between these 2 simple ECG parameters and their effect on CRT has not been systematically assessed in a large-scale clinical trial. Methods and Results— The Resynchronization–Defibrillation for Ambulatory Heart Failure Trial showed that implantable cardioverter defibrillator-CRT was associated with a significant reduction in the primary end point of all-cause mortality or heart failure hospitalization. For this substudy, we excluded patients in atrial fibrillation and those with a previous pacemaker. All baseline ECGs were reviewed by a panel of 3 experienced electrocardiographers. A total of 1483 patients were included in this study. Of these, 1175 had left bundle-branch block (LBBB) and 308 had non-LBBB. In patients with LBBB receiving implantable cardioverter defibrillator-CRT, there was a reduction in the primary outcome and in each individual component of the primary outcome. Furthermore, there was continuous relationship between QRS duration and extent of benefit. In patients with non-LBBB and QRS ≥160 ms, the hazard ratio for the primary outcome was 0.52 (0.29–0.96; P =0.033); in patients with QRS <160 ms, the hazard ratio was 1.38 (0.88–2.14; P =0.155). Conclusions— In patients with LBBB, there was a continuous relationship between broader QRS and greater benefit from implantable cardioverter defibrillator-CRT. However, our data do not support the use of implantable cardioverter defibrillator-CRT in patients with non-LBBB, especially when the QRS duration is <160 ms. There may be some delayed benefit when the QRS is ≥160 ms, but this needs further investigation. Clinical Trial Registration— URL: . Unique identifier: [NCT00251251][1]. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00251251&atom=%2Fcirchf%2F6%2F6%2F1190.atom

Usefulness of mean platelet volume as a biomarker for long-term outcomes after percutaneous coronary intervention.

Larger size platelets have enhanced reactivity. The mean platelet volume (MPV) is a marker of platelet activation and is usually measured as part of blood testing. The aim of the present study was to investigate the utility of the MPV as a biomarker in prognosticating the long-term outcomes after percutaneous coronary intervention (PCI). The baseline MPV values from consecutive patients undergoing PCI were screened. Of the 1,432 patients, the composite primary end point of mortality or myocardial infarction at 1 year occurred in 80 (5.6%). The patients in the highest tertile (MPV >9.1 fL) had an increased frequency of the primary end point compared to those in the mid (8.1 to 9.1 fL) and lowest (<8.1 fL) tertiles (9.0%, 4.5%, and 3.5%, respectively; p <0.01). Logistic regression analysis demonstrated diabetes (odds ratio 2.44, 95% confidence interval 1.48 to 4.00) and highest tertile of MPV (odds ratio 2.42, 95% confidence interval 1.47 to 3.99) as the best predictors of adverse outcomes. In patients with acute coronary syndrome, the preprocedural MPV and troponin levels demonstrated a comparable predictive relation to the primary end point (receiver operator characteristics curve analysis, area under the curve 0.64, p = 0.01; and 0.63, p = 0.01, respectively). In conclusion, an elevated MPV was a strong independent predictor of long-term outcomes after PCI. The preprocedural MPV had prognostic value similar to that of troponin in patients with acute coronary syndrome. These findings could be of importance in the clinical evaluation of patients before PCI and the design of future studies assessing antiplatelet therapies.

Localized rotational activation in the left atrium during human atrial fibrillation: Relationship to complex fractionated atrial electrograms and low-voltage zones

BACKGROUND In humans, the existence of rotors or reentrant sources maintaining atrial fibrillation (AF) and the underlying electroanatomic substrate has not been well defined. OBJECTIVE Our aim was to determine the prevalence of localized rotational activation (RotA) in the left atrium (LA) during human AF and whether complex fractionated atrial electrograms (CFAEs) or low-voltage areas colocalize with RotA sites. METHODS We prospectively studied 32 patients (mean age 57 ± 8 years; 88% with persistent AF) undergoing AF catheter ablation. Bipolar electrograms were recorded for 2.5 seconds during AF using a roving 20-pole circular catheter in the LA. RotA was defined as sequential temporal activation of bipoles around the circular catheter. Bipolar electrogram fractionation index and bipolar voltage were used to define CFAEs and low-voltage areas, respectively. RESULTS In 21 (66%) patients, 47 RotA sites were identified. Few (9%) lasted 2.5 seconds (cycle length 183 ± 6 ms), while the majority (91%) were nonsustained (duration 610 ± 288 ms; cycle length 149 ± 11 ms). RotA was most common in the pulmonary vein antrum (71%) and posterior LA (25%). CFAEs were recorded from 18% ± 12% of LA area, and most (92% ± 7%) were not associated with RotA sites. However, 85% of RotA sites contained CFAEs. Very low voltage (<0.1 mV) areas comprised 12% ± 10% of LA area and were present in 23% of RotA sites. CONCLUSIONS In patients with predominantly persistent AF, localized RotA is commonly present but tends to be transient (<1 second). Although most CFAEs do not colocalize with RotA sites, the high prevalence of CFAEs and very low voltages within RotA sites may indicate slow conduction in diseased myocardium necessary for their maintenance.

Cardiac resynchronization therapy in patients with left ventricular systolic dysfunction and right bundle branch block: A systematic review

BACKGROUND Whether patients with right bundle branch block (RBBB) benefit from cardiac resynchronization therapy (CRT) is unclear. OBJECTIVE The purpose of this study was to systematically review the published data from randomized clinical trials of CRT on the outcomes in patients with baseline RBBB. METHODS Randomized controlled trials of CRT in heart failure and left ventricular systolic dysfunction were identified from MEDLINE (1950-2010), EMBASE (1980-2010, week 45), Cochrane Controlled Trials Register (2009), Cochrane Database of Systematic Reviews, National Institutes of Health Clinical Trials.gov database. RESULTS A total of 112 references were retrieved. Four publications from five studies reported data on patients with RBBB and were included in this investigation, with 259 patients randomized to CRT and 226 randomized to non-CRT. None of the available data showed more favorable outcomes (soft or hard) in patients with CRT. CONCLUSION None of the available data showed more favorable outcomes with CRT in patients with RBBB. A meta-analysis of RBBB patients from the major CRT trials is urgently needed. Results of the meta-analysis can direct further research, perhaps indicating a need for randomized trials in RBBB. Physicians and patients should be aware of the likely reduced benefit form CRT in patients with RBBB, and this should be factored into decision making. However, until more data are available it is too early to change guidelines.

Subclinical Atrial Fibrillation in Older Patients.

Background: Long-term continuous electrocardiographic monitoring shows a substantial prevalence of asymptomatic, subclinical atrial fibrillation (SCAF) in patients with pacemakers and patients with cryptogenic stroke. Whether SCAF is also common in other patients without these conditions is unknown. Methods: We implanted subcutaneous electrocardiographic monitors (St. Jude CONFIRM-AF) in patients ≥65 years of age attending cardiovascular or neurology outpatient clinics if they had no history of atrial fibrillation but had any of the following: CHA2DS2-VASc score of ≥2, sleep apnea, or body mass index >30 kg/m2. Eligibility also required either left atrial enlargement (≥4.4 cm or volume ≥58 mL) or increased (≥290 pg/mL) serum NT-proBNP (N-terminal pro–B-type natriuretic peptide). Patients were monitored for SCAF lasting ≥5 minutes. Results: Two hundred fifty-six patients were followed up for 16.3±3.8 months. Baseline age was 74±6 years; mean CHA2DS2-VASc score was 4.1±1.4; left atrial diameter averaged 4.7±0.8 cm; and 48% had a prior stroke, transient ischemic attack, or systemic embolism. SCAF ≥5 minutes was detected in 90 patients (detection rate, 34.4%/y; 95% confidence interval [CI], 27.7–42.3). Baseline predictors of SCAF were increased age (hazard ratio [HR] per decade, 1.55; 95% CI, 1.11–2.15), left atrial dimension (HR per centimeter diameter, 1.43; 95% CI, 1.09–1.86), and blood pressure (HR per 10 mm Hg, 0.87; 95% CI, 0.78–0.98), but not prior stroke. The rate of occurrence of SCAF in those with a history of stroke, systemic embolism, or transient ischemic attack was 39.4%/y versus 30.3%/y without (P=0.32). The cumulative SCAF detection rate was higher (51.9%/y) in those with left atrial volume above the median value of 73.5 mL. Conclusions: SCAF is frequently detected by continuous electrocardiographic monitoring in older patients without a history of atrial fibrillation who are attending outpatient cardiology and neurology clinics. Its clinical significance is unclear. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01694394.

Predictors of Fracture Risk of a Small Caliber Implantable Cardioverter Defibrillator Lead

Introduction: The Sprint Fidelis 6949 implantable cardioverter defibrillator (ICD; Medtronic Inc., Minneapolis, MN, USA) lead has a high rate of fracture. Identification of predictors of subsequent fracture is useful in decision making about lead replacement and for future lead design. We sought to determine if there are clinical, procedural, or radiological features associated with a greater risk of subsequent lead fracture.

Health-Related Quality of Life in Patients With Atrial Fibrillation Treated With Rhythm Control Versus Rate Control Insights From a Prospective International Registry (Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation: RECORD-AF)

Background—Improving health-related quality of life (HRQoL) is an important treatment goal in the management of patients with atrial fibrillation (AF). Uncertainty exists as to whether patients’ HRQoL differ when treated with medical rhythm control or rate control. We compared HRQoL between patients treated with rhythm control or rate control in a large observational registry of patients with recent-onset AF. Methods and Results—In the Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation (RECORD-AF), 2439 patients with recent onset (<1 year) AF completed an AF-specific HRQoL questionnaire, the University of Toronto Atrial Fibrillation Severity Scale. HRQoL was assessed by the AF symptom severity score (0–35, with higher scores reflecting more severe AF-related symptoms) at baseline and 1 year. The minimal clinically important difference was defined as a change of ≥3 points. The primary analysis was based on a propensity score-adjusted longitudinal regression analysis which compared the change in AF symptom severity scores between the 2 groups. Over an average follow-up of 1 year, the AF symptom severity scores improved in both groups (rhythm control: −2.82 point [95% confidence interval, −3.22 to −2.41]; rate control: −2.11 point [95% confidence interval, −2.54 to −1.67]; P<0.01 for both groups). The magnitude of improvement was higher in the rhythm control group than the rate control group (unadjusted difference: −0.75 point; 95% confidence interval, −1.31 to −0.19; P=0.01; propensity score-adjusted difference: −0.71 point; 95% confidence interval, −1.31 to −0.11; P=0.02). Conclusions—In this observational cohort of recent-onset AF patients, treatment with medical rhythm- or rate control over 1 year was associated with an improvement in HRQoL. The magnitude of HRQoL improvement was minimally higher in patients treated with rhythm control than rate control. However, the overall degree of improvement was not large, and its clinical significance was uncertain.

Canadian Heart Rhythm Society and Canadian Association of Radiologists consensus statement on magnetic resonance imaging with cardiac implantable electronic devices.

Magnetic resonance imaging (MRI) has historically been considered contraindicated for individuals with cardiac implantable electronic devices (CIEDs) such as pacemakers and implantable defibrillators. Magnetic resonance scanners produce magnetic fields that can interact negatively with the metallic components of CIEDs. However, as CIED technology has advanced, newer MRI conditional devices have been developed that are now in clinical use and these systems have had demonstrated safety in the MRI environment. Despite the supportive data of such CIED systems, physicians remain reluctant to perform MRI scanning of conditional devices. This joint statement by the Canadian Heart Rhythm Society and the Canadian Association of Radiologists describes a collaborative process by which CIED specialists and clinics can work with radiology departments and specialists to safely perform MRI in patients with MRI conditional CIED systems. The steps required for patient and scanning preparation and the roles and responsibilities of the CIED and radiology departments are outlined. We also briefly outline the risks and a process by which patients with nonconditional CIEDs might also receive MRI in highly specialized centres. This document supports MRI in patients with MRI conditional CIEDs and offers recommendations on how this can be implemented safely and effectively.

In Vivo Assessment of Myocardial Glucose Uptake by Positron Emission Tomography in Adults With the PRKAG2 Cardiac Syndrome

Background—The PRKAG2 cardiac syndrome is an inherited metabolic disease of the heart characterized by excessive myocardial glycogen deposition. The biochemical alterations associated with this condition remain controversial and have not previously been studied in affected humans. Methods and Results—Positron emission tomography (PET) imaging was used to quantitatively assess myocardial glucose uptake (MGU) in 6 adult subjects with the PRKAG2 cardiac syndrome and 6 healthy, matched control subjects using the glucose analogue 18F-Fluoro-2-deoxyglucose (FDG). Studies were performed under a euglycemic hyperinsulinemic clamp to ensure stable blood glucose levels. Rubidium-82 perfusion scans were performed to ensure that myocardial differences in myocardial glucose uptake were not the result of significant myocardial scar. In adult patients with phenotypic expression of disease, the median myocardial glucose uptake of the left ventricle was 0.18 &mgr;mol/min/g (interquartile range, 0.14, 0.24), compared with 0.40 &mgr;mol/min/g (interquartile range, 0.30 to 0.45) in the control group (P=0.01). The median blood glucose during FDG-PET imaging was 4.72 mmol/L (interquartile range, 4.32 to 4.97) in the PRKAG2 group and 4.38 mmol/L (interquartile range, 3.90, 4.79) in the control group (P=NS). The significant decrease observed in myocardial glucose uptake in affected patients occurred in the absence of significant myocardial scar. Conclusions—The PRKAG2 cardiac syndrome is associated with a reduction of glucose uptake in adult patients affected with this genetic condition. In this pilot study, 18F-FDG-PET imaging is a useful tool to assess alterations in myocardial glucose transport in this inherited metabolic disease and provide insight into the biochemical pathophysiology of the diseased state.