Letter from the Editor

Door-to-Balloon Time (DTB) "Putting the Cath Lab's Role in Perspective"

Morton Kern, MD
Morton Kern, MD
When finally asked specifically about this latter patient, I informed our quality assurance people of the following. The patient was an 82-year-old man with two days of stuttering chest pain, anterior ST elevations with some coving, borderline blood pressure, diminished peripheral pulses, and a systolic heart murmur. This patient required careful review in addition to aggressive STEMI management. The cath procedure was complicated by tortuous iliac arteries and abdominal aortic disease, three-vessel coronary artery disease (CAD) with TIMI-3 flow in the infarct-related left anterior descending (LAD) artery, and surprisingly, a 40 mmHg gradient across the aortic valve. I also performed a left ventricular (LV) gram followed by abdominal aortography before deciding on whether or what kind of intervention to undertake. The ejection fraction turned out to be 25%. After careful consideration of options, emergency coronary artery bypass graft surgery (CABG) versus percutaneous coronary intervention (PCI), I stented the LAD to treat the STEMI and assist in LV functional recovery in preparation for an eventual and necessary aortic valve replacement and CABG surgery to come. Is there any wonder why I had a long door-to-balloon time? Fortunately, there was TIMI-3 flow in the infarct-related artery already. Was a short DTB time an appropriate outcome measure for this particular patient? This example highlights the major problem with the DTB time as a marker of quality, skill, system function and outcome. The pressure exerted upon all elements of the system (ambulance, ER, and cath lab) to treat the STEMI patient and improve outcomes by achieving a short (1,2 McNamara RL and colleagues published results from 29,222 patients from 395 hospitals participating in the National Registry of Myocardial Infarction who were treated within 6 hours of presentation. Longer DTB times had higher mortality rates (3.0, 4.2, 5.7 and 7.4% for 150 minutes, respectively).1 However admirable this goal, this pressure should not suppress the need for good judgment and good care. The DTB time must be put into perspective; namely, that the patient always comes first. The DTB is promoted by hospitals and physicians as a marketing tool, a surrogate indicator of a quality system. As Dr. Ralph Brindis succinctly and expertly stated in a American College of Cardiology Cardiosource editorial, entitled The Challenges and Pitfalls of Door-to-Balloon Time as a Performance Metric, while highly admirable, the DTB should not be considered the only marker but one of several indicators of quality for the treatment of the STEMI patient.3 An issue which is also troubling is what should constitute the actual balloon time used as the indicator for reperfusion. For example, if the patient has TIMI-3 flow, i.e., already achieved full reperfusion, does the balloon need to be used? Should the clock stop after guidewire crossing if TIMI-3 flow occurs? Should the clock stop if the balloon is inflated and nothing happens to the flow? What if the balloon was advanced and inflated but not in the infarct artery? Should the clock stop if a thrombectomy catheter is needed before balloon inflation? What about a patient who is transferred for care from elsewhere with STEMI? These are questions yet to be answered, but add confusion to the true intent of the DTB time which acts as one of the strongest reminders to us to get the artery open as quickly as possible. Fortunately, I have not seen nor heard of physicians or hospitals in my area trying to game the system by not appropriately assessing potentially important co-morbid conditions such as aortic dissection, or making poor clinical decisions in the management of cardiogenic shock by not initially stabilizing the patient with IABP prior to directing attention to the culprit coronary artery, or avoiding fibrinolytic therapy based on an anticipated prolonged DTB time. Because of the pressure of this system, the cath lab must endure a certain few false positive emergency catheterization call-ins for presumed STEMI due to inaccurate or uninterpretable 12-lead ECG interpretations with early activation of the on-call catheterization staff. What can the cath lab do to shorten DTB time? The cath lab’s role in achieving shorter DTB times has been discussed extensively in the cardiology literature.2,4 The cath lab should concentrate on factors that are under their control and assist others in controlling those factors that are related to the door-to-balloon time for the STEMI patient (see table on previous page). In summary, the cath lab can make a big difference in the lives of our STEMI patients but should understand the limits of the rush to the door.
References
1. McNamara RL, Wang Y, Herrin J, et al., on behalf of the NRMI Investigators. Effect of door-to-balloon time on mortality in patients with ST-segment elevation myocardial infarction. J Am Coll Cardiol 2006;47:2180-2186.

2. Jacobs AK, Antman EM, Ellrodt G, et al., on behalf of the American Heart Association’s Acute Myocardial Infarction Advisory Working Group. Recommendation to develop strategies to increase the number of ST-segment-elevation myocardial infarction patients with timely access to primary percutaneous coronary intervention. Circulation 2006;113: 2152-2163.

3. Brindis RG. The Challenges and Pitfalls of Door-to-Balloon Time as a Performance Metric. Cardiosource. Accessed August 3, 2006. http://www.cardiosource.com/editorials/index.asp?EdID=83#4. Henry TD, Atkins JM, Cunningham MS, et al. ST-segment elevation myocardial infarction: recommendations on triage of patients to heart attack centers: is it time for a national policy for the treatment of ST-segment elevation myocardial infarction? J Am Coll Cardiol 2006;47:1339-1345