Strategies for detecting cardiac sources of embolism after ischemic stroke

Detecting the probable cause of ischemic stroke is one of the main goals of the diagnostic evaluation of ischemic stroke patients. Various causes of stroke require specific treatment changes that can lower the risk of recurrent stroke. However, after the first in-hospital analysis, no cause of stroke is detected in about 25% of patients. Because several cardiac diseases can be a cause of ischemic stroke, this group of patients undergoes additional cardiac evaluation.
This thesis aims to evaluate the use of routine cardiac investigations for the detection of major cardiac sources of embolism (CSE) in patients with ischemic stroke or TIA of undetermined cause, and to find possibilities for improvement of the current strategy.

Part one focuses on the detection of atrial fibrillation (AF). We show that the use of an automated detection algorithm for AF during in-hospital heart rhythm monitoring improves AF detection in stroke patients. After hospital discharge, ambulatory heart rhythm monitoring further increases the rate of AF detection. In addition, longer monitoring duration leads to higher detection rates. These results support extending the current guideline-recommended monitoring period of three days to at least seven days.

Part two concentrates on the detection of structural CSEs with transthoracic echocardiography (TTE). Currently, in the Netherlands, the availability of TTE is limited due to shortage of experienced echocardiographers. When combining data from our systematic review and meta-analysis, retrospective single-center study, and prospective multicenter study, we can conclude that routine TTE in patients with ischemic stroke or TIA of undetermined cause infrequently detects a major CSE, in about 1% of patients. The majority of these patients also had major abnormalities on their electrocardiogram (ECG). Results of a subsequent cost-effectiveness analysis show that the strategy of only selecting patients with such ECG-abnormalities for TTE is cost-effective compared to performing TTE in all patients with ischemic stroke or no patients. Thus, a strategy that only selects patients with major ECG-abnormalities to undergo TTE would therefore be more efficient, reduce the amount of unnecessary TTE examinations and consequently reduce pressure on the Dutch healthcare system.