The translation and implementation of evidence-based medicine into clinical practice is under increasing scrutiny by clinicians and healthcare stakeholders. Clearly, everyone would agree that to achieve the best clinical outcomes, proven therapies or treatment strategies should be implemented whenever or however possible. In an attempt to make the assessment of this process simple as well as objective, various performance measurements or goals have been established such as the Centers for Medicare & Medicaid Services/Joint Commission on Accreditation of Healthcare Organizations (CMS/JCAHO) Core Measures. Many of these core measures relate to the management of acute myocardial infarction and include the use of aspirin, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors in patients with depressed left ventricular (LV) function as well as "door-to-drug" time for ST-segment elevation myocardial infarction (STEMI). An additional CMS/JCAHO core measure receiving great interest is the door-to-balloon (D2B) time in patients undergoing primary percutaneous coronary intervention (PCI) for STEMI care. It is hoped that by focusing attention on all of these performance measures, clinical care and outcomes will be improved.
The recent 2004 American College of Cardiology/American Heart Association (ACC/AHA) Clinical Guidelines for STEMI care and the 2005 AHA/ACC/Society for Cardiac Angiography and Interventions (SCAI) PCI Clinical Guidelines "tightened" the recommendation for D2B in primary PCI to <90 minutes as a Class 1A recommendation. The guidelines further endorsed care patterns surrounding the "first medical contact" or the use of a hospital transfer strategy to utilize primary PCI in STEMI management with a Class 1A recommendation of a "first medical contact-to-balloon" <90 minutes.[2,3]
Various government agencies and other healthcare stakeholders are now expecting clinicians and hospitals to meet these performance standards. Pressure to meet these expectations is being applied using a variety of strategies including public reporting of individual hospital adherence to performance measures, Centers of Excellence designations, and Pay-for-Performance initiatives. This has motivated clinicians and hospitals to focus significant resources on efforts to achieve D2B times <90 minutes, with the ultimate benefit of improving clinical outcomes and saving lives.
Intense scrutiny of the D2B metric in the present environment has, however, demonstrated multiple shortcomings in this process despite this being a seemingly "easy to measure" concrete performance measure. In addition, examples of negative "unintended consequences" of the public reporting of outcomes are beginning to surface and have gained attention among those interested in promoting the quality of care. Because of the interest in improving the care of patients with STEMI, it is critical that D2B times be assessed and reported appropriately.[4,5]
Weaknesses of the D2B Performance Measure
In reality, D2B time comes at the end of a sequence of events for the patient who is suffering a STEMI. The ideal metric is the "symptom onset to reperfusion time" and there are many opportunities to shorten this interval. The D2B measure fails to account for the patient variable of symptom recognition and the introduction of the patient into the medical care system ideally through EMS activation. Unfortunately, despite active public education, only about 50% of patients with STEMI arrive to hospitals via ambulance, which can obscure proper triage of these patients.
At present, patient clinical confounders are not fully accounted for in the D2B metric that would appropriately "prolong" the performance of this time metric including:
Delays in obtaining patient or family permission for instituting care.
Necessity to exclude alternative/complicating diagnoses such as aortic dissection, pulmonary embolus, pericarditis, or malignancy.
Emergent treatment/stabilization of the patient with complicating ventricular tachycardia or cardiogenic shock, etc.
The CMS/JCAHO D2B performance measure excludes "transferred patients" and therefore does not measure the "first door" D2B time. Therefore, it does not allow true opportunities for the healthcare system to evaluate the wisdom of a transfer primary PCI strategy rather than timely fibrinolytic therapy.
Important clinical issues occurring in the cardiac catheterization laboratory compounding difficulties in assessment and utilization of the D2B metric include:
Clinical imperative of stabilization of patients with cardiogenic shock with intra-aortic balloon counterpulsation (IABP) prior to performing coronary angiography and "delaying" the PCI.>
Issues surrounding challenging vascular access due to peripheral arterial disease.
What exactly is the "balloon time?"
Is it attainment of TIMI 3 flow (problem of "no-reflow" often seen post-stent placement)?
Could it occur with wire crossing and subsequent attainment of TIMI 3 flow?
Is it balloon inflation with or without TIMI 3 flow? (There have been anecdotal reports of "gaming" by some operators inflating angioplasty balloons in the aorta or in a "nonculprit" portion of the coronary artery!)
Stent placement rather than predilatation with balloon?
Use of intracoronary thrombectomy devices attaining TIMI 3 flow with or without follow-up stent placement?
Negative Unintended Consequences of Applying the D2B Metric
Unfortunately, despite the interest of all cardiovascular healthcare stakeholders in improving STEMI care at the bedside, increasing anecdotal reports have arisen as a consequence of the implementation of the D2B metric including:
"Short-tracking" clinical processes of care by not appropriately assessing potentially important co-morbid conditions such as aortic dissection, etc., leading to poor clinical outcomes.
Poor clinical decision making in the management of cardiogenic shock by not initially stabilizing the patient with IABP prior to directing attention to the culprit coronary artery.
Transferring a patient to another institution for STEMI management despite having the hospital resources available on-site when realizing that the patient in question would have a D2B time or door-to-needle (D2N) time that would be a significant outlier of >120 minutes. (This scenario actually has occurred.)
Due to the lack of a CMS/JCAHO measure for the "percentage of appropriate use of a reperfusion strategy in eligible patients," a hospital or physician might opt to not attempt to reperfuse a given STEMI patient by either fibrinolytic therapy or primary PCI, based on an anticipated prolonged D2N or D2B time.
The percentage of "false positive" emergency catheterizations for presumed STEMI may increase due to inaccurate "in the field" 12-lead ECG interpretations and early activation of catheterization on-call staff.
The D2B Metric Going Forward
National quality and outcome experts as well as healthcare stakeholders are now participating in discussions to ensure that this important metric, D2B, be defined crisply and not be allowed to become a "fuzzy metric" subject to criticism and manipulation. Patients excluded from this metric must be clearly defined and records of facilities submitting data must be subject to external auditing. Furthermore, this process must proceed in a manner that minimizes the chance for unintended negative consequences. This most likely should include a target threshold of a median (not mean) D2B of possibly 75% of patients <90 minutes, which would allow for the needed "wiggle room" to account for the appropriate management of "clinical confounders" when clinically justified.
Don't Throw out the Balloon "Baby" With the Bath Water Although the D2B metric is not yet perfect, it is in fact a solid indicator of system performance in the assessment of STEMI systems of care for primary PCI, particularly with the measure enhancement using the median time rather than mean time of D2B. Timely utilization of primary PCI for STEMI <90 minutes of first medical contact is both a reasonable and desirable goal based on a large body of substantial evidence from multiple clinical trials and national registries.[2,3,6] Under guidance of our nation's outcomes leaders, the D2B metric is continuing to evolve and improve. We must maintain our focus on the patient and the desire to deliver the highest quality evidence-based care. Issues surrounding the D2B measure briefly discussed here should not distract clinicians and hospitals from our goal of improving timely access and implementing all the evidence-based therapy shown to be beneficial for our patients with acute myocardial infarctions.
Special thanks and recognition go to Greg Dehmer, Harlan Krumholz, Eric Peterson, and Fred Masoudi for their superb and expert advice and edits of this editorial.
Cardiosource © 2006 American College of Cardiology
The author's comments express his or her personal opinions and do not necessarily reflect the official position of the American College of Cardiology.
Cite this: The Challenges and Pitfalls of Door-to-Balloon Time as a Performance Metric - Medscape - Jun 14, 2006.