The data from randomized trials were inconsistent on the appropriate dosing of heparin in patients undergoing diagnostic procedures through radial artery access. Our meta-analysis of available randomized trials showed that the 5000 Units of heparin, compared to lower doses resulted in a trend toward a lower risk of radial artery occlusion, a trend toward higher risk of hematoma and increased radial artery compression time.
To our knowledge, this is the first and largest systematic review and meta-analysis of randomized controlled trials comparing various doses of heparin in transradial access. A previous study with a total of 4 studies (with both randomized and non-randomized trials) showed superiority of 5000 Units compared to lower dose in reduction of radial artery occlusion. Our meta-analysis is strengthened by larger of number randomized trials, exploration of other outcomes of interest and performance of subgroup analyses for different sheath size and different doses of heparin.
As the interventionalists are increasingly using radial access instead of femoral access for coronary procedures due to significant reduction in access-related complications and mortality especially in patients with ST segment elevation myocardial infarction (STEMI), the incidence of RAO may rise further, which calls for the approaches to reduce radial artery occlusion in these patients. Among various approaches to reduce RAO, heparin use is commonly practiced approach to maintain RA patency post-procedure; therefore, our study is an effort to study the appropriate dosing of heparin.
The potential mechanism of radial artery occlusion consists of occlusive and non-occlusive injury . Endothelial dysfunction, intimal tear and hyperplasia, medial calcification and adventitial inflammation are patterns of non-occlusive injury whereas thrombus formation is occlusive injury. The prevention of radial artery occlusion entails different interventions and techniques, heparin administration being one of them.
The current meta-analysis is limited by small number of randomized trials and lack of patient level data. Significant heterogeneity was observed in some of the outcomes, which could not be lowered despite subgroup analyses. One study reported significantly higher rates of RAO. Meta-regression could not be performed due to small number of studies (< 10). Nevertheless, the current study is strengthened by inclusion of all available randomized trials comparing various doses of heparin in patients undergoing coronary angiography.