Piyush Ojha, MBBS, MD, DM

Petersen NH, Ortega-Gutierrez S, Wang A, Lopez GV, Strander S, Kodali S, et al. Decreases in Blood Pressure During Thrombectomy Are Associated With Larger Infarct Volumes and Worse Functional Outcome. Stroke. 2019;50:1797–1804

Recent studies have shown that acute ischemic stroke patients with large vessel occlusion (LVO) have good clinical outcome following endovascular thrombectomy (EVT), which is now a new standard of care. However, only 46% of patients undergoing EVT were functionally independent (mRS 0-2) at 90 days, and only 10% were neurologically normal in the meta-analysis of EVT trials [Highly Effective Reperfusion evaluated in Multiple Endovascular Stroke Trials (HERMES)].1 Several factors could potentially contribute to this observation. Both clinical and imaging variables have been shown to correlate with poor outcome, especially age, stroke severity, lack of effective reperfusion and infarct volume.  

Management of blood pressure is hotly debated in the stroke literature. There are theoretical concerns and benefits of acute blood pressure lowering in acute ischemic stroke. Blood pressure fluctuations during EVT could lead to inadequate cerebral perfusion causing poor final radiological (infarct progression) and clinical outcomes (functional status) in patients with LVO. Hypotension prior to reperfusion may compromise collateral flow, which may be further worsened by the exhaustion of compensatory vasodilatory capacity distal to the occluded vessel and the loss of intrinsic autoregulatory function in the ischemic tissue leading to a poor clinical and radiological outcome. 

In the present study, Petersen et al.2 assessed the effects of blood pressure reduction and sustained relative hypotension during EVT on clinical and radiological outcomes. The authors retrospectively analysed consecutive acute ischemic stroke patients (>18 years, Anterior circulation) due to LVO (ICA or MCA i.e. M1 or M2), who underwent EVT. Intraprocedural mean arterial pressure (MAP) was monitored throughout the procedure. ∆MAP was calculated as the difference between admission MAP and lowest MAP during EVT until recanalization. Sustained hypotension was measured as the area between admission MAP and continuous measurements of intraprocedural MAP (aMAP). MRI Brain at 24 hours was done to estimate final infarct volume, and functional outcome determined by modified Rankin Scale score (mRS) [favourable outcome 0-2, unfavourable outcome 3-6] at discharge and 90 days.

The study included 397 patients (mean age 71±14 years, mean NIHSS 17), out of which 72% achieved TICI 2b/3 reperfusion. Mean MAP was 105±18 and 114±21 mm Hg, on admission and arrival in the angio suite, respectively. 87% of patients experienced reductions in MAP during EVT. The average maximum MAP reduction (∆MAP) was 31±20 mm Hg.

Good outcome was associated with younger age, male sex, lower NIHSS on admission, tPA administration prior to EVT, degree of reperfusion and fewer comorbidities. Patients with unfavourable outcome had a higher mean ∆MAP and ∆SBP compared with those with favourable outcome. ∆MAP was independently associated with worse clinical outcome (mRS) at discharge and at 90 days after adjusting for age, ASPECTS score, baseline BP, admission NIHSS, TICI score, and onset-to-reperfusion time. For every 10 mm Hg reduction in MAP, there was a 22% increased likelihood of shifting towards worse outcomes on the mRS at 90 days. The association between aMAP and outcome was also significant at discharge and 90 days.

The authors also observed a significant association between ∆MAP and aMAP with the infarct growth and final infarct volume. After adjusting for age, admission NIHSS, TICI score, and core infarct volume, ∆MAP remained independently associated with infarct growth (P=0.036) and final infarct volume (P=0.035). Although the majority (65%) of the EVT were done under conscious sedation, which has been associated with greater hemodynamic stability compared with general anaesthesia, frequent and substantial reductions in blood pressure were observed in the study.

The authors, hence, concluded that blood pressure reductions and sustained relative hypotension during EVT were independent predictors of worse functional outcome at discharge and 90 days, supporting the hypothesis that the cerebral perfusion pressure is integral for survival of the ischemic penumbra.

The strength of the study was the large sample size involving 2 large academic stroke centres. However, there were several limitations, i.e., retrospective analysis, exclusion of posterior circulation stroke, target lower BP and BP monitoring methods not clearly defined and that all the patients not achieving the desired successful reperfusion.

Although the existing guidelines suggest that hypotension and hypovolemia should be managed appropriately for maintaining the cerebral perfusion, a single BP target below 180/105 mm Hg for all patients is insufficient for the management of the patients. Hence, future prospective, randomised trials evaluating blood pressure management in the acute ischemic stroke patients due to LVO would be useful to further strengthen the association of blood pressure fluctuations and clinico-radiological outcome in these patients.  

References:

  1. Goyal M, Menon BK, van Zwam WH, Dippel DW, Mitchell PJ, Demchuk AM, et al; HERMES collaborators. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials. Lancet. 2016;387:1723–1731.
  2. Petersen NH, Ortega-Gutierrez S, Wang A, Lopez GV, Strander S, Kodali S, et al. Decreases in Blood Pressure During Thrombectomy Are Associated With Larger Infarct Volumes and Worse Functional Outcome. Stroke. 2019;50:1797–1804.