Page 33 - Cardiac abnormalities after aneurysmal subarachnoid hemorrhage

Impact of cardiac complications on outcome after aneurysmal subarachnoid hemorrhage
One study defined QT prolongation as more than 410 milliseconds, whereas others
have used a cut-off value of more than 460 milliseconds. T wave abnormalities
included both T wave inversion and T wave flattening. U waves were defined as
present, greater than 1 mm or as negative U waves. Moreover, some studies did not
provide criteria for abnormalities at all. This obviously might influence reported
prevalence of cardiac abnormalities and influence effect of cardiac abnormalities on 2 outcome.
Third, most studies investigated echocardiography, biochemical markers and ECG abnormalities separately. Therefore, the relative contribution and incremental prognostic value of the different cardiac abnormalities is uncertain. The combinations of several ECG abnormalities have been studied, and three studies found that the combination of different ECG abnormalities better predicts prognosis than the individual variables alone.
Fourth, as the cardiac abnormalities are reversible, with unknown time course, the timing of cardiac evaluation could influence results. Only a few of the included studies performed serial cardiac studies with predefined time intervals. The importance of the timing of cardiac investigations in relation to the outcome of SAH is highlighted in one study, in which the authors found a difference in prognostic value of elevated troponin levels on day four versus day nine after onset of SAH. LV dysfunction showed the same trend, although the criteria for LV dysfunction were different between these two days.
Fifth, the baseline characteristics of the included studies and the prevalence of the cardiac determinants and outcomes showed a large variation. Percentage of men varied from 22 to 62%, follow-up duration varied from in-hospital follow-up to six months, and poor condition on admission varied from 23 to 68%. This might indicate differences in study populations and therefore influences results.
Six, the quality of the included articles varied as reflected in the STROBE score, which varied between 11 and 20 points (out of 22 points) with a median of 17. This may also partly explain the heterogeneity of results.
Finally, the heterogeneity of the different clinical severity scores and the thresholds used to dichotomize the various scales and the timing of the assessment may be a factor.
The shortcomings of the included studies stress the need for large prospective, observational studies with clearly defined methodology, sufficient sample size, and long-term follow-up to assess whether cardiac abnormalities have independent prognostic value after SAH.
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