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Posts Tagged ‘cardiac MRI’

MRI in Patients with Cardiac Devices

Nazarian et al report on the safety of MRI in patients with cardiac devices.

Abstract

BACKGROUND

Patients who have pacemakers or defibrillators are often denied the opportunity toundergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria specified by the Food and Drug Administration (termed “MRI-conditional” devices).

METHODS

We performed a prospective, nonrandomized study to assess the safety of MRI at a
magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter–defibrillator (42%) that was not considered to be MRI-conditional (termed a “legacy” device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters).

RESULTS

No long-term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patient’s device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients. At long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in
4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming.

CONCLUSIONS

We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter–defibrillator system. No long-term clinically significant adverse events were reported.

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Late Gadolinium Enhancement in Dilated Cardiomyopathy

Halliday et al (Circulation. 2017;135:2106–2115. DOI: 10.1161/CIRCULATIONAHA.116.026910) report on the relationship between late gadolinium enhancement on cardiac MRI and sudden cardiac death in patients with dilated cardiomyopathy. They identify a subgroup with LVEF \ge 40% at increased risk of sudden cardiac death.

Abstract

BACKGROUND

Current guidelines only recommend the use of an implantable
cardioverter defibrillator in patients with dilated cardiomyopathy for the primary prevention of sudden cardiac death (SCD) in those with a left ventricular ejection fraction (LVEF) 35%. Patients with an LVEF >35% also have low competing risks of death from nonsudden causes. Therefore, those at high risk of SCD may gain longevity from successful implantable cardioverter defibrillator therapy. We investigated whether late gadolinium enhancement (LGE) cardiovascular magnetic resonance identified patients with dilated cardiomyopathy without severe LV systolic dysfunction at high risk of SCD.

METHODS

We prospectively investigated the association between midwall LGE and the prespecified primary composite outcome of SCD or aborted SCD among consecutive referrals with dilated cardiomyopathy and an LVEF ≥40% to our center between January 2000 and December 2011 who did not have a preexisting indication for implantable cardioverter defibrillator implantation.

RESULTS

Of 399 patients (145 women, median age 50 years, median LVEF 50%, 25.3% with LGE) followed for a median of 4.6 years, 18 of 101 (17.8%) patients with LGE reached the prespecified end point, compared with 7 of 298 (2.3%) without (hazard ratio [HR], 9.2; 95% confidence interval [CI], 3.9–21.8; P<0.0001). Nine patients (8.9%) with LGE compared with 6 (2.0%) without (HR,4.9; 95% CI, 1.8–13.5; P=0.002) died suddenly, whereas 10 patients (9.9%) with LGE compared with 1 patient (0.3%) without (HR, 34.8; 95% CI, 4.6–266.6; P<0.001) had aborted SCD. After adjustment, LGE predicted the composite end point (HR, 9.3; 95% CI, 3.9–22.3; P<0.0001), SCD (HR, 4.8; 95% CI, 1.7–13.8; P=0.003), and aborted SCD (HR, 35.9; 95% CI, 4.8–271.4; P5% compared with those without LGE were 10.6 (95% CI, 3.9–29.4), 4.9 (95% CI, 1.3–18.9), and 11.8 (95% CI, 4.3–32.3), respectively.

CONCLUSIONS

Midwall LGE identifies a group of patients with dilated cardiomyopathy and an LVEF ≥40% at increased risk of SCD and low risk of nonsudden death who may benefit from implantable cardioverter defibrillator implantation.

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Area: Height Ratio in Patients With Proximal Ascending Aortic Dilation and Trileaflet Aortic Valve

Masri et al report an observational longitudinal study of patients with proximal dilation of the ascending aorta and trileaflet aortic valves. The authors report the relationship between ascending aortic area to height ration (as assessed by CT or MRI) and clinical outcome.

Abstract

BACKGROUND:

In patients with a dilated proximal ascending aorta
and trileaflet aortic valve, we aimed to assess (1) factors independently
associated with increased long-term mortality and (2) the incremental
prognostic utility of indexing aortic root to patient height.

METHODS:

We studied consecutive patients with a dilated aortic root (≥4
cm) that underwent echocardiography and gated contrast-enhanced thoracic
aortic computed tomography or magnetic resonance angiography between
2003 and 2007. A ratio of aortic root area over height was calculated
(cm2/m) on tomography, and a cutoff of 10 cm2/m was chosen as abnormal,
on the basis of previous reports. All-cause death was recorded.

RESULTS:

The cohort comprised 771 patients (63 years [interquartile range,
53–71], 87% men, 85% hypertension, 51% hyperlipidemia, 56% smokers).
Inherited aortopathies, moderate to severe aortic regurgitation, and severe
aortic stenosis were seen in 7%, 18%, and 2%, whereas 91% and 54% were
on β-blockers and angiotensin-converting enzyme inhibitors, respectively.
Aortic root area/height ratio was ≥10 cm2/m in 24%. The Society of
Thoracic Surgeons score and right ventricular systolic pressure were 3.3±3
and 31±7 mm Hg, respectively. At 7.8 years (interquartile range, 6.6–8.9),
280 (36%) patients underwent aortic surgery (76% within 1 year) and 130
(17%) died (1% in-hospital postoperative mortality). A lower proportion of
patients in the surgical (versus nonsurgical) group died (13% versus 19%,
P<0.01). On multivariable Cox proportional hazard analysis, aortic root area/
height ratio (hazard ratio, 4.04; 95% confidence interval [CI], 2.69–6.231)
was associated with death, whereas aortic surgery (hazard ratio, 0.47;
95% CI, 0.27–0.81) was associated with improved survival (both P<0.01).
For longer-term mortality, the addition of aortic root area/height ratio ≥10
cm2/m to a clinical model (Society of Thoracic Surgeons score, inherited
aortopathies, hypertension, hyperlipidemia, medications, aortic regurgitation,
and right ventricular systolic pressure), increased the c-statistic from 0.57
(95% CI, 0.35–0.77) to 0.65 (95% CI, 0.52–0.73) and net reclassification
index from 0.17 (95% CI, 0.02–0.31) to 0.23 (95% CI, 0.04–0.34), both
P<0.01. Of the 327 patients with aortic root diameter between 4.5 and 5.5
cm, 44% had an abnormal aortic root area/height ratio, of which 78% died.

CONCLUSIONs:

In patients with dilated aortic root and trileaflet aortic
valve, a ratio of aortic root area to height provides independent and
improved stratification for prediction of death.

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