Page for the General Public

The following pages summarize and review this issue’s articles for an audience without a background in medicine or research.

Sotiris C. Stamou et al.: “Axillary Versus Femoral Arterial Cannulation During Repair of Type A Dissection? An Old Problem Seeking New Solutions.”

Patients who undergo surgery for acute type A aortic dissection, a potentially life threatening disruption of the wall layers of the body’s main artery, need to be put on cardiopulmonary bypass while the surgeon operates on the heart. During cardiopulmonary bypass, the patient’s circulation is supported by a heart-lung machine, allowing to stop the heart for the procedure. To lead the blood from the heart-lung machine into the body, a large cannula (or tube) has to be inserted into one of the major vessels of the body. In acute type A dissection, the most commonly used vessels are the femoral artery in the groin and the axillary artery close to the axilla. There is an ongoing debate which of these vessels should be preferred, and a variety of previous studies have shown opposing results. Sotiris C. Stamou et al. conducted a study on 305 patients that were operated on for acute type A dissection. They concluded that the choice of vessels does not influence survival of the patient neither in the first days after surgery nor at long-term. The more relevant factors that influenced survival in their study were instability of the patient before surgery, length of the procedure, age and postoperative complications such as stroke. The authors therefore conclude that the vessel for cardiopulmonary bypass should be chosen on an individual basis, depending on surgeon preference, vessel calcifications and other risk factors. As every study, the study has certain limitations. Theefore, further research is necessary to reach a valid answer to the question.

Alexander E. Curtis et al.: “The Mystery of the Z-Score”

“The mystery of the Z-Score” by Curtis et al. is a state of the art review on a measuring method called Z-score, which can be calculated and applied to a variety of measurements. It shows how much a certain measurement deviates from the average of a normal reference population. Z-scores are an alternative to standard diameter measurement e.g. when evaluating the size of the aorta, the body’s main artery. Since the body surface area can be included in the calculation, it is especially useful when evaluating the aorta of children. Children grow quickly, and growth of their aorta needs to be put in relation to their body size. However, the Z-score has limitations as well, including measurement errors, different body surface area formulas and uncertainties regarding the correct normal reference values and their changes with age. Ethnical and geographical differences need to be taken into account as well. Therefore, Z-scores need to be applied with caution to these limitations. Future studies are needed to investigate the abovementioned limitations, especially focusing on the natural history of the Z-score in normal and pathological states to improve its reliability in clinical decision making.