Impact of Defibrillator Electrode Placement on Outcome of Electrical Cardioversion of Atrial Fibrillation: A Pilot Observational Study.

BACKGROUND: Anterior-posterior electrode placement is preferred in electrical cardioversion of atrial fibrillation. However, the optimal anterior-posterior electrode position in relation to the heart is not studied. METHODS AND RESULTS: We performed a prospective observational study on patients presenting for cardioversion of atrial fibrillation. Electrodes were placed in the anterior-posterior position and shock was delivered in a step-up approach (100 J→200 J→360 J). Fluoroscopic images were obtained, and distances were measured from points A, midanterior electrode; and B, midposterior electrode, to midpoint of the cardiac silhouette. Patients requiring one 100 J shock for cardioversion success (group I) were compared with those requiring >1 shock/100 J (group II). Logistic regression was used to determine the impact of electrode distance on low energy (100 J) cardioversion success. Computed tomography scans from this cohort were analyzed for anatomic landmark correlation to the cardiac silhouette. Of the 87 patients included, 54 (62%) comprised group I and 33 (38%) group II. Group I had significantly lower distances from the mid-cardiac silhouette to points A (5.0±2.4 versus 7.4±3.3 cm; P<0.001) and B (7.3±3.0 versus 10.0±3.8 cm; P=0.002) compared with group II. On multivariate analysis, higher distances from the mid-cardiac silhouette to point A (odds ratio, 1.33 [95% CI, 1.07-1.70]; P=0.01) and B (odds rsatio, 1.24 [95% CI, 1.05-1.50]; P=0.01) were independent predictors of low energy (100 J) cardioversion failure. Based on review of computed tomography scans, we suggest that the xiphoid process may be an easy landmark to guide proximity to the myocardium. CONCLUSIONS: In anterior-posterior electrode placement, closer proximity to the cardiac silhouette predicts successful 100 J cardioversion irrespective of clinical factors.

Valve-in-Mitral Annular Calcification Transcatheter Mitral Valve Replacement After Thrombosis of Extracardiac Valved Conduit.

We report a patient with severe mitral annular calcification, mitral stenosis/regurgitation, hypertrophic obstructive cardiomyopathy, and subaortic membrane treated with valved left atrium-left ventricle conduit, septal myectomy, and membrane resection. Subsequent thrombosis of the conduit prompted successful valve-in- mitral annular calcification transcatheter mitral valve replacement and laceration of the anterior mitral leaflet to prevent outflow obstruction. (Level of Difficulty: Advanced.).

Clinical Use of CT-Derived Fractional Flow Reserve in the Emergency Department.

OBJECTIVES: This study sought to examine the feasibility, safety, clinical outcomes, and costs associated with computed tomography-derived fractional flow reserve (FFRCT) in acute chest pain (ACP) patients in a coronary computed tomography angiography (CTA)-based triage program. BACKGROUND: FFRCT is useful in determining lesion-specific ischemia in patients with stable ischemic heart disease, but its utility in ACP has not been studied. METHODS: ACP patients with no known coronary artery disease undergoing coronary CTA and coronary CTA with FFRCT were studied. FFRCT ≤0.80 was considered positive for hemodynamically significant stenosis. RESULTS: Among 555 patients, 297 underwent coronary CTA and FFRCT (196 negative, 101 positive), whereas 258 had coronary CTA only. The rejection rate for FFRCT was 1.6%. At 90 days, there was no difference in major adverse cardiac events (including death, nonfatal myocardial infarction, and unexpected revascularization after the index visit) between the coronary CTA and FFRCT groups (4.3% vs. 2.7%; p = 0.310). Diagnostic failure, defined as discordance between the coronary CTA or FFRCT results with invasive findings, did not differ between the groups (1.9% vs. 1.68%; p = NS). No deaths or myocardial infarction occurred with negative FFRCT when revascularization was deferred. Negative FFRCT was associated with higher nonobstructive disease on invasive coronary angiography (56.5%) than positive FFRCT (8.0%) and coronary CTA (22.9%) (p < 0.001). There was no difference in overall costs between the coronary CTA and FFRCT groups ($8,582 vs. $8,048; p = 0.550). CONCLUSIONS: In ACP, FFRCT is feasible, with no difference in major adverse cardiac events and costs compared with coronary CTA alone. Deferral of revascularization is safe with negative FFRCT, which is associated with higher nonobstructive disease on invasive angiography.

Plaque disruption by coronary computed tomographic angiography in stable patients vs. acute coronary syndrome: a feasibility study.

AIMS: This study was designed to determine whether coronary CT angiography (CTA) can detect features of plaque disruption in clinically stable patients and to compare lesion prevalence and features between stable patients and those with acute coronary syndrome (ACS). METHODS: We retrospectively identified patients undergoing CTA, followed by invasive coronary angiography (ICA) within 60 days. Quantitative 3-vessel CTA lesion analysis was performed on all plaques ≥25% stenosis to assess total plaque volume, low attenuation plaque (LAP, <50 HU) volume, and remodelling index. Plaques were qualitatively assessed for CTA features of disruption, including ulceration and intra-plaque dye penetration (IDP). ICA was employed as a reference standard for disruption. A total of 145 (94 ACS and 51 stable) patients were identified. By CTA, plaque disruption was evident in 77.7% of ACS cases. Although more common among those with ACS, CTA also detected plaque disruption in 37.3% of clinically stable patients (P < 0.0001). CONCLUSIONS: Clinically stable patients commonly manifest plaques with features of disruption as determined by CTA. Though the prevalence of plaque disruption is less than patients with ACS, these findings support the concept that some clinically stable patients may harbour 'silent' disrupted plaques. These findings may have implications for detection of 'at risk' plaques and patients.

CT dose reduction using prospectively triggered or fast-pitch spiral technique employed in cardiothoracic imaging (the CT dose study).

OBJECTIVES: To establish current radiation dose levels with contemporary scanners capable of prospectively triggered or high-pitch spiral scan modes to previous generation scanners among patients evaluated for coronary artery disease, pulmonary embolism, aortic disease, and "triple rule out" in a large population of patients at multiple centers. BACKGROUND: Previous small-scale studies with carefully controlled scan protocols report that CT scanners that facilitate prospectively triggered scanning and provide high-pitch spiral CT scan modes drastically lower radiation doses. However, diagnostic reference levels should be selected by medical bodies on the basis of large surveys of representative sites and reviewed at appropriate time intervals. METHODS: Scan data including dose and image quality parameters were collected retrospectively from 64 slice scanners (control) and prospectively after sites installed 128-slice dual-source scanners with high-pitch capability (study). Protocol selection was purposely not specified to survey "real world" results. Blinded quantitative image analysis was performed on every fifth scan. RESULTS: From April 2011 to March 2012, 2085 patients at 9 sites completed the study: 1051 coronary artery disease (509 control, 542 study), 528 pulmonary embolism (267 control, 261 study), 419 aortic disease (268 control, 151 study), and 87 triple rule out (53 control, 34 study). There was a significant reduction in median dose-length product (DLP) from 669 mGy ∙ cm (interquartile range [IQR]: 419-1026 mGy ∙ cm) in the control group to 260 mGy ∙ cm (IQR: 159-441 mGy ∙ cm) in the study group, a reduction by 61% (P < .0001) and was lower in all categories. No significant differences were noted in image quality. CONCLUSION: Use of advanced scanners facilitating prospectively triggered or high-pitch spiral scan modes results in marked dose reduction across a variety of cardiovascular studies, with no compromise in image quality. These findings may contribute to new target dose recommendations in societal guidelines.

Prospective radial artery study following induction of reactive hyperemia looking at degree of diameter growth in healthy subjects.

OBJECTIVES: This "proof of concept" study sought to determine the magnitude of radial artery diameter change in 20 healthy subjects by induction of flow mediation dilatation (FMD) via reactive hyperemia. BACKGROUND: Transradial access in the cardiac catheterization laboratory is becoming more commonplace due to lower bleeding complications and increase in patient comfort. However, access to the radial artery can be challenging due to small vessel size. We sought to examine whether FMD can be used to increase radial artery diameter, potentially allowing improved transradial access. METHODS: We obtained baseline radial artery diameter via a high frequency ultrasound probe on 20 healthy subjects. A standard reactive hyperemia protocol was employed in the right arm, followed by successive measurements of the subject's radial artery at pre-specified intervals. Radial artery diameter measurements were performed offline by the sonographer and also a blinded reader to which agreement was sought. RESULTS: We found a mean increase in radial artery size of 0.48 ± 0.13 mm at peak reactive hyperemic states. This correlated to a mean increase in overall radial artery diameter of 21.7 ± 6.7%. The median time to peak dilation was 30 seconds (95% CI; 15-45 seconds), and the median duration of maximal dilation was 60 seconds (95% CI; 45-75 seconds). CONCLUSIONS: Among healthy subjects, we demonstrated a mean maximal increase in radial artery diameter of 21.7 ± 6.7% via FMD. This finding supports the notion that radial artery diameter can be increased noninvasively via a reactive hyperemia protocol.