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Glyceryl trinitrate does not improve outcomes of ischemic stroke

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Prehospital trials pose particular challenges

The RIGHT-2 trial shows the limitations of a prehospital enrollment model, wrote Karen C. Johnston, MD, professor of neurology at the University of Virginia in Charlottesville, and Valerie L. Durkalski-Mauldin, PhD, professor of medicine at Medical University of South Carolina in Charleston, in an editorial accompanying the RIGHT-2 trial results. The rate of nonstroke diagnoses was so high that it would have reduced the study’s power to assess the efficacy of glyceryl trinitrate (GTN), had the investigators not increased the sample size and changed the statistical analysis plan.

“Future prehospital trials need to consider the implications of enrolling, yet excluding, stroke mimics in the primary analysis,” said Dr. Johnston and Dr. Durkalski-Mauldin. Using telemedicine in the ambulance to facilitate direct contact between the stroke provider and the patient and emergency medical services provider could reduce the enrollment of patients with stroke mimics in clinical trials, they added. “Improved tools to exclude stroke mimics in the field have been difficult to develop and validate. The absence of imaging in most ambulances will continue to limit field personnel from definitively determining ischemic stroke from intracerebral hemorrhage, which will limit hyperacute trials to interventions presumed safe in both populations.”

In addition, the blood pressure reduction that GTN provided might not be clinically relevant, said Dr. Johnston and Dr. Durkalski-Mauldin. “The RIGHT-2 investigators report no difference in blood pressure at day 3 or day 4 of treatment, which might have been related to the very low adherence to study protocol by day 4.

“Regardless of these limitations, RIGHT-2 has provided high-level evidence that GTN given within 4 hours of onset does not significantly improve outcome in hyperacute patients presenting with possible stroke,” the authors concluded (Lancet. 2019 Feb 6. doi: 10.1016/

S0140-6736(19)30276-4). Dr. Johnston and Dr. Durkalski-Mauldin declared no conflicts of interest.


 

REPORTING FROM ISC 2019

Administering glyceryl trinitrate (GTN) early after onset of ischemic stroke or transient ischemic attack (TIA) does not improve outcomes, according to data presented at the International Stroke Conference sponsored by the American Heart Association. Results suggest that GTN causes adverse effects in patients with intracerebral hemorrhage (ICH), but this observation is not definitive, according to the researchers. Study results were published online ahead of print Feb. 6 in the Lancet.

Nitric oxide is a regulatory molecule that has vasoactive effects and promotes blood pressure reduction. Vascular levels of nitric oxide are low in stroke, which suggests that the molecule may be a target for stroke treatment. GTN, a nitric oxide donor, lowered blood pressure and improved functional outcome among patients with acute stroke in the phase 2 Rapid Intervention with GTN in Hypertensive Stroke Trial (RIGHT).

Philip Bath, MD, Stroke Association Professor of Stroke Medicine at the University of Nottingham (England), and colleagues conducted the RIGHT-2 study to evaluate the safety and efficacy of GTN when administered early after onset of suspected stroke. Paramedics randomized patients in equal groups to a GTN patch or a sham patch in the ambulance. Three more patches were administered in the hospital on the following days. Active and sham patches looked similar and had no writing on them, thus ensuring effective blinding upon administration. Investigators followed up patients by telephone at 90 days to assess the modified Rankin Scale score and markers of disability, mood, cognition, and quality of life.

Eligible participants were adults who had dialed emergency services, independently or with assistance, because of a possible stroke. They had a Face, Arm, Speech, Time (FAST) score of 2 or 3, were within 4 hours of onset, and had a systolic blood pressure greater than 120 mm Hg. Patients from nursing homes, those with hypoglycemia, those who were unconscious, and those with a witnessed seizure were excluded.

Dr. Bath and colleagues planned to enroll 850 patients from five ambulance services in 30 hospitals across the United Kingdom. Data were to be examined through an intention-to-treat analysis. During the trial, however, the investigators observed that the rate of stroke mimics was 26%, rather than the 12% that they had anticipated. To ensure the proper power for the study, the investigators increased the sample size to 1,149 patients. They also changed the planned data analysis from intention-to-treat to hierarchical analysis. Specifically, the researchers planned to perform the primary analysis in patients with stroke or TIA. If the results were positive, then they would perform a standard intention-to-treat analysis.

More than 99% of patients received the first patch. Approximately 57% of the population received the first two patches. One reason for this decrease in adherence was that many patients were discharged from the hospital with a TIA or a stroke mimic. Participants’ average age was 72. The median time from onset to randomization was 71 minutes, and the median time to treatment was 73 minutes. Participants’ mean systolic blood pressure was 162 mm Hg. Approximately 60% of the patients had a FAST score of 3. About 50% of participants had ischemic stroke, 13% had ICH, 10% had TIA, and 26% had stroke mimics.

At 1 hour after treatment initiation, systolic blood pressure decreased by 6.2 mm Hg and diastolic blood pressure decreased by 2.7 mm Hg among patients who received GTN, compared with controls. At one day, the differences were 5.2 mm Hg and 2.5 mm Hg, respectively, in treated patients, compared with controls. Blood pressure became similar between groups thereafter, “in part because of the tachyphylaxis that we know happens with GTN,” said Dr. Bath.

The researchers found no evidence of an effect of GTN on functional outcome at 90 days in participants with stroke or transient ischemic attack. The adjusted common odds ratio of poor outcome was 1.25 in the GTN group, compared with the control group (95 % confidence interval, 0.97-1.60; P = .083). “We were close to getting a negative trial,” said Dr. Bath.

Subgroup analyses revealed differences in outcome according to the time to randomization. GTN had a negative effect in patients treated within 1 hour of onset. Results were neutral, but tended to be negative, in patients treated between 1 and 2 hours of onset. Results were neutral, but tended to be positive, among patients treated at more than 2 hours after onset. There was no difference between groups in the rate of mortality.

One of the study’s limitations was its single-blind design. In addition, the trial was conducted in a single country, and the investigators changed the protocol after it was initiated. “We had a higher-than-expected [stroke] mimic rate, although I’m reassured by most experts that ... this is probably about right,” said Dr. Bath.

A potential reason for the neutral results is the negative effect that GTN had among patients with ICH, said Dr. Bath. “In that very early first hour, we are of course breaking a law that we learned in medical school, which is that the first part of hemostasis is spasm. We gave an antispasmodic: a vasodilator,” he added. “That is speculation.”

The trial was funded by the British Heart Foundation. Dr. Bath declared a modest ownership interest in Platelet Solutions and consultant or advisory board positions with Moleac, DiaMedica, Phagenesis, Nestle, and ReNeuron. The other investigators declared no conflicts of interest.

SOURCE: Bath PM et al. ISC 2019, Abstract LB2.

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