MRI safe for most patients with Pacemakers or Defibrillators

A study by Russo et al published in the NEJM found that MRI scans for patients with older not FDA approved pacemakers and implantable cardioverter-defibrillators (ICD) are safe even if the scan focuses on the chest area.

The researchers performed 1000 MRI in which patients had a pacemaker and in 500 MRI in which patients had an ICD in a 1.5T MRI scanner. 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.  Nine of the implants were disrupted but reset themselves to backup mode.  In all but one instance the effect was temporary.

Neither MRI performed on chest or in other parts of the body produced significant complications.   The concerns of potential magnetic field–induced cardiac lead heating, which could result in myocardial thermal injury and/or disrupt pacing properties of the devices were noted in this study.

The authors concluded that in their study, device or lead failure did not occur in any patient who was appropriately screened, and had the device reprogrammed in accordance with the pre-specified protocol.

Gene test reveals which women with breast cancer do not need chemotherapy

Research by Sparano et al published in the NEJM suggests that the gene test known as Oncotype DX may help women with early stage breast cancer avoid chemotherapy.

The authors performed a prospective trial involving women with hormone-receptor–positive, HER2–negative, axillary node–negative breast cancer with tumors of 1.1 to 5.0 cm in the greatest dimension (or 0.6 to 1.0 cm in the greatest dimension and intermediate or high tumor grade). The Oncotype DX assay of 21 genes was performed on the tumor tissue, and the results were used to calculate a score indicating the risk of breast-cancer recurrence; patients were assigned to receive endocrine therapy without chemotherapy if they had a recurrence score of 0 to 10 on a scale 1 to 100, indicating a very low risk of recurrence.

Of the 10,253 eligible women enrolled, 1626 women (15.9%) who had a recurrence score of 0 to 10 were assigned to receive endocrine therapy alone without chemotherapy. At 5 years, in this patient population, the rate of invasive disease–free survival was 93.8%, the lack of metastasis at a distant site was 99.3%, and the rate of overall survival was 98.0%.

The authors concluded that patients with hormone-receptor–positive, HER2-negative, axillary node–negative breast cancer, those with tumors that had a favorable gene-expression profile the test accurately identified the group of women whose cancers are likely to respond to hormone-blocking drugs and adding chemo would do little if any good while exposing them to side effects and other health risks.  The researchers found that patients who skipped chemo based on the test had a small chance of cancer recurrence at 5 years with endocrine therapy alone.

Complications of Central Venous Catheterization by Insertion Site

Parienti et al report in NEJM the finds of a trial regarding complications from central venous catheters depending on the insertion site. 

In this multicenter trial, they randomly assigned non-tunneled central venous catheterization in patients in the intensive care unit to the subclavian, jugular, or femoral veins.

The primary outcome measure was catheter-related bloodstream infection and symptomatic deep-vein thrombosis.

A total of 3471 catheters were inserted in 3027 patients. In the three-choice comparison, there were 8, 20, and 22 primary outcome events in the subclavian, jugular, and femoral groups, respectively (1.5, 3.6, and 4.6 per 1000 catheter-days; P=0.02). In pairwise comparisons, the risk of the primary outcome was significantly higher in the femoral group than in the subclavian group and in the jugular group than in the subclavian group, whereas the risk in the femoral group was similar to that in the jugular group. In the three-choice comparison, pneumothorax requiring chest-tube insertion occurred in 13 (1.5%) of the subclavian-vein insertions and 4 (0.5%) of the jugular-vein insertions.

The authors concluded that subclavian vein catheterization was associated with a lower risk of bloodstream infection and symptomatic thrombosis and a higher risk of pneumothorax than jugular vein or femoral vein catheterization.

N Engl J Med 2015; 373:1220-1229

Anatomical versus Functional Testing for Coronary Artery Disease

Douglas et al in their article in NEJM compared the outcomes of anatomical versus functional tests in patients with coronary artery disease. 

They randomly assigned 10,003 symptomatic patients to an initial anatomical testing with the use of coronary computed tomographic angiography (CTA) or to functional testing (exercise electrocardiography, nuclear stress testing, or stress echocardiography). The composite primary end point was death, myocardial infarction, hospitalization for unstable angina, or major procedural complication. Secondary end points included invasive cardiac catheterization that did not show obstructive CAD and radiation exposure.

The mean age of the patients was 60.8±8.3 years, 52.7% were women, and 87.7% had chest pain or dyspnea on exertion. The mean pretest likelihood of obstructive CAD was 53.3±21.4%. Over a median follow-up period of 25 months, a primary end-point event occurred in 164 of 4996 patients in the CTA group (3.3%) and in 151 of 5007 (3.0%) in the functional-testing group. CTA was associated with fewer catheterizations showing no obstructive CAD than was functional testing (3.4% vs. 4.3%, P=0.02), although more patients in the CTA group underwent catheterization within 90 days after randomization (12.2% vs. 8.1%). The median cumulative radiation exposure per patient was lower in the CTA group than in the functional-testing group (10.0 mSv vs. 11.3 mSv), but 32.6% of the patients in the functional-testing group had no exposure, so the overall exposure was higher in the CTA group (mean, 12.0 mSv vs. 10.1 mSv; P<0.001).

In symptomatic patients with suspected CAD who required noninvasive testing, a strategy of initial CTA, as compared with functional testing, did not improve clinical outcomes over a median follow-up of 2 years suggesting that patients with chest pain have no less risk of heart attack, dying or being hospitalized than those who take a simple stress test.  

Mechanical Thrombectomy in Ischemic Strokes; the MR CLEAN trial

Berkhemer et al report in NEJM the results of a Multicenter Randomized Clinical Trial of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands (MR CLEAN) that included patients with severe stroke and proximal-vessel occlusion.  The patients with acute ischemic stroke were randomly assigned to receive intra-arterial treatment plus usual care or usual care alone. Eligible patients had a proximal arterial occlusion in the anterior cerebral circulation that was confirmed on vessel imaging and could be treated within 6 hours after the onset of symptoms.

The primary outcome was evaluated based on the modified Rankin scale score at 90 days; this categorical scale measures functional outcome, with scores ranging from 0 (no symptoms) to 6 (death).

The study involved 500 stroke patients whose mean age was 65 years (23-96).  They were treated at 16 medical centers in the Netherlands with 233 assigned to intraarterial treatment while 267 to usual care alone.   Before the randomization 445 of (89.0%) were treated with intravenous alteplase, a tissue plasminogen activator. Retrievable stents were used to snare and remove the thrombus in 190 of the 233 patients (81.5%) assigned to intra-arterial treatment.  There was an absolute difference of 13.5 percentage points in the rate of functional independence (modified Rankin score, 0 to 2) in favor of the intervention (32.6% vs. 19.1%) after three months. There were no significant differences in mortality or the occurrence of symptomatic intracerebral hemorrhage about 19% in both groups at one month.

They concluded that in patients with acute ischemic stroke caused by a proximal intracranial occlusion of the anterior circulation, intra-arterial treatment administered with a mechanical device within 6 hours after stroke onset was effective and safe.