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Dr. Shun Kohsaka is with the Department of Cardiology at Keio University School of Medicine in Tokyo, Japan. He recently co-authored a paper, published in the June issue of the Japanese Circulation Society's Circulation Journal, titled “Barriers Associated With Door-to-Balloon Delay in Contemporary Japanese Practice.”

This important study demonstrated that the Japanese median door-to-balloon (DTB) time was 90 minutes during the study period (2008 to 2013), signaling that half of the STEMI patients did not achieve the recommended DTB time or 90 minutes or less.

Angioplasty.Org's partner site, TCROSS NEWS, recently interviewed Dr. Kohsaka regarding the background of this study and its implications for organizational and clinical management of STEMI patients.

    Shun Kohsaka, MD
Shun Kohsaka, MD

Q: What is the KiCS Registry?
Dr. Kohsaka: KiCS stands for Keio inter-hospital Cardiovascular Studies, and is a collaborative working group in the field of cardiology at Keio University and its related hospitals. The KiCS network was founded in 2002 and started its first multi-center registry in 2008. We currently study and analyze quality and outcome in modern cardiology practice. Keio University established a graduate school of medicine in clinical research in 2012 and so far nearly 70 English-language articles have been published from the group.

Q: The present study showed that the median DTB time was 90 min and that 46.2% of the patients exceeded that DTB time. What is your opinion about this finding?
Dr. Kohsaka: Given consideration of the study period (between 2008 and 2013), the result of median DTB time in this study is not far from reality. The CREDO-KYOTO registry, another multi-center Japanese registry (the study period between 2005 and 2007) also demonstrated the same DTB time (90 min). However, median DTB time was reported as 42 min in the J-AMI study initiated by the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT). However, as we mentioned in the article, that registry has a potential selection bias, and therefore those findings must be interpreted with caution.

A previous study for the U.S. reported median DTB time as 86 min. Approximately half of patients did not reach DTB time of less than 90 min. In order to reduce DTB time, both public and private sectors studied how to cope with and improve the situation. As a result, more than 90% of the AMI cases have now achieved DTB time of less than 90 min. I hope that the outcome in the present study catches the attention of the Japanese public and private sectors as it did in the U.S.

Q: In your study, there is no significant change in median DTB time from the previous period (2008 to 2009) and 2013, but rather DTB time actually increased from 85 min to 90 min. Also, no improvement was observed in the hospital mortality. How do you explain this?
Dr. Kohsaka: The trend of DTB was not statistically significant, but it is to be taken as no big deal. The present study did not analyze causal relationship between in-hospital mortality and DTB, and thereby their causal relationship in Japan is uncertain. Data from the U.S. revealed that shorter DTB time related to better prognosis. So far, there is no room for doubt in this finding.

Today, the Japanese Circulation Society (JCS) strongly recommends minimizing DTB time (<90 min). Additionally the reimbursement rate has changed since 2013.

Q: Was there any difference between low-volume centers and high-volume centers in mortality rates for DTB time of <90 min or DTB time >90 min?
Dr. Kohsaka: Because the present study focused on predictors of DTB time more than 90 min, we did not analyze causal relationship between in-hospital mortality and DTB. To pursue this outcome, conducting a study with a larger data set is required.

Q: The KiCS registry demonstrated that the Japanese median DTB time (90 min) is longer than U.S. (63 min). In the Discussion section, the investigators emphasized its improvement. So, why is the Japanese DTB time so long?
Dr. Kohsaka: Coronary artery disease is the number one killer in the United States, and therefore improvement of prognosis had been the largest challenge in their society.

The relationship between short DTB time and a favorable prognosis has been demonstrated, resulting in introducing the Pay for Performance (P4P) system which aimed at DTB time. Under the P4P system, a management team in each hospital gathered together to intervene on various issues. The effort was not only made by hospitals, but also involved emergency services in each district. In addition, the American Heart Association (AHA) declared and announced the public “Mission Lifeline”. Based upon these efforts made throughout the country, the United States achieved DTB time of less than 90 min in 90% of the cases.

However, some hospitals took advantage of DTB time in their advertising, increasing unnecessary calls from an emergency department to a heart team as well as fraud reports.

Q: When DTB time <90 min is not achieved, the reimbursement rate for each procedure is cut by 29%. Your study showed that nearly half of the hospitals failed to achieve DTB time of <90 min. Is it a matter of life and death in certain hospitals? And what improvements are necessary for these hospitals?
Dr. Kohsaka: Prognosis is more important for the patient than the reimbursement rate. We have no idea how the P4P system affect the Japanese clinical practice, so that further studies are needed to find its advantages.
Q: It has been criticized that too many hospitals perform PCI in Japan as compared to the U.S. What is the link between this point of view and the present study.
Dr. Kohsaka: You are right. Indeed, the number of PCI centers in Japan are outstanding. Limited resources are not equally available in each hospital; therefore, efforts to improve quality indicators such as DTB time should be made by limited number of medical practitioners. Like in France, it is not realistic to eliminate low-volume PCI centers (<400 cases per year) in Japan. So, each management team in each hospital needs to put effort into reducing DTB time. Medical care in an acute phase for the STEMI patient is established by three processes including: (1) Pre-hospital (to arrival); (2) Emergency room; and (3) Catheterization laboratory. Hospitals with DTB time of more than 90 min should focus on their processes for better care.

This interview was conducted in June 2017 by TCROSS NEWS, Tokyo, Japan