Evaluation of Minimally Invasive Subcortical Parafascicular Access for Clot Evacuation

Aurora Health Care is serving as the coordinating center and will prepare Standard Operating Procedures to address registry operations and analysis activities, such as patient recruitment, data collection, data management, data analysis, and reporting for adverse events.

Sites will identify, recruit, obtain consent for subjects and collect data using standard forms; these activities will be monitored remotely by the coordinating site. Data from the participating hospitals will be checked for heterogeneity, queried and subsequently pooled. Baseline patient characteristics and demographics, Hemphill and Essen predictive scores, NIHSS stroke severity score, functional status from the Barthel index and mRS score, and ICH volumetric assessments, will be presented as means, medians, or proportions, as appropriate. Eligibility and consent rates will be derived for each center.

Analyses will be largely descriptive in nature. Follow-up assessments at 30 and 90 days, for composite outcome of death or disability (defined as mRS>2), and death and disability separately, will be described with proportions. Tallies of surgical complications will also be derived as separate outcomes.

Analysis of 30- and 90-day status will entail an informal comparison for the purposes of providing preliminary evidence and for planning of a larger comparative trial. The proportion of patients under experimental treatment who suffer from death or dependency at 30-days, as determined by cutoffs on the modified Rankin Scale with exact binomial upper and lower 90% confidence limits will be used in a comparison to our criteria of: (1) 65% (historical proportion of patients under medical management, unselected for baseline risk), and (2) 50% (proportion of patients under other minimally invasive surgical techniques unselected for baseline risk). This confidence limit comparative approach provides a flexible method of assessment of non-inferiority, equivalence, and superiority. The unselected population will, however, be a mix of patients at different levels of baseline risk, and so a follow-up stratified analysis will be conducted if counts permit. The unselected population will be matched using demographics, lesion characteristics and comorbidities as close as possible to the study group. A heterogeneity index will be used for comparison. As a corollary to this analysis, baseline predictive scores (translated from scores to percentages/risks) will be used to calculate expected counts of 30 and 90 day status stratified within the 0-3 range of the Hemphill ICH score and 0-10 range of the Essen ICH score, and these expected counts will be compared to observed counts using a Fisher Exact Test.

Fifty (50) patients were chosen as a convenient sample size, based on enrollments from all of the participating hospitals, with recruitment accomplished in a reasonable timeframe of 2 years. About 65% of unselected patients with ICH (that is, not stratified by baseline predicted risk) have a documented 30- day composite outcome of death or dependency under medical management. Reviews of other types of minimallyinvasive ICH surgeries provide evidence of significantly improved outcomes (meta-analysis odds ratio 0.54 (0.39, 0.76)). An odds ratio of 0.54 indicates a reduction in risk from 65% to about 50% (15% absolute reduction).

Assuming the new procedure is truly at least as effective as other minimally invasive surgeries (50% 30-day composite outcome risk), and therefore 15% more effective than conventional management, 50 patients provides 66% surity that a 95% 1-sided confidence interval will exclude the chance that the new procedure is worse than medical management.

An alternative method of framing this, based on an exact one-sided binomial test of a one-sample proportion and an alpha level of 5%, is that a sample size of 50 patients provides approximately 66% surity/power that the new procedure is superior to medical management (i.e., lower than 65% suffering from death or poor functional outcomes). The computed critical value for this test, to provide some initial evidence of superiority, is observing no more than 26 patients (out of 50) suffering from death or dependency under the new surgical procedure. The surity/power of 66% used as an assumption above is permissive. The study size and preliminary nature of the results will not be sufficient to perform robust statistical testing for superiority or non-inferiority of the new parafascicular ICH-evacuation technique, though results from this registry will provide a crucial first look at effectiveness, and health costs.