Preoperative medical optimization prior to surgery for hip fractures frequently requires balancing the benefits of potential medical interventions with complications arising from prolonged immobilization. Several previous studies have found that a prolonged duration to surgery (≥ 48 hours) for hip fractures may increase the 30-day and 1-year mortality rates [9, 10]. However, patients suffering from hip fractures usually are elderly, fragile, and have many pre-existing medical conditions. Thus, it is a frequent practice that preoperative consultation with another service is obtained for risk stratification and medical optimization. While the goal is to make a decision to proceed or medically optimize the patient first, the process of preoperative medical evaluation usually takes 1 to 2 days before heading to surgery . Among the common preoperative examinations, the dipyridamole-based thallium scan may require a longer duration to organize, which is often dependent on scanner availability and time of day [12–15], and a 4-day average delay was seen at our institution.
If a thallium scan would affect the risk of postoperative complications, and if further selective preoperative treatment such as coronary angiography may be required, postoperative cardiac complications may be reduced by balancing the risks in the two groups. Thus, we utilized the propensity score-matching technique to balance the differences in baseline conditions and comorbidities between the groups and to minimize the selection bias caused by retrospective cohort study. The results of our study suggested that the rate of 90-day cardiac complications was still high despite the use of a dipyridamole-thallium scan (19.47% vs. 15.58%, Fig. 1). Utilization of preoperative dipyridamole-thallium scanning was not significantly associated with a change in the 90-day overall cardiac complications (OR = 1.32; 95% CI 0.75 to 2.33; p = 0.332, Table 2) or mortality (adjusted OR = 0.75; 95% CI 0.08 to 6.71; p = 0.797) after correcting the confounding factors in the multivariate analysis. Further subgroup evaluation of patients with postoperative unstable angina and acute myocardial infarction was performed, which also showed no statistically significant differences between the two groups (p = 0.437 and 0.272, respectively). We found that patients with ASA grade ≥ 3 and pre-existing cardiac comorbidities (ischemic heart disease, congestive heart failure, and valvular heart disease) were associated with an increased risk of 90-day cardiac complications. Furthermore, among the patients who underwent a thallium scan, only one (4.3%) had myocardial infarction after surgery, and no mortality was observed within the postoperative 90 days. Our results suggested that the performance of a thallium scan was not predictive of cardiac complications, despite delaying surgery for an average of 4 days.
Ricci et al.  demonstrated that preoperative cardiac testing (dipyridamole-thallium scanning, echocardiography, and cardiac catheterization) did not change the management of perioperative orthopedic surgery or medical therapy in elderly patients with hip fractures, but did incur a huge cost of over $47 million annually in the United States, with a delay to surgery of on average 3.3 days, as compared with 1.9 days. Multiple studies have also demonstrated that preoperative cardiac testing with echocardiography delays surgery without a significant change in preoperative cardiac medications or anesthesia [11, 17–19]. In addition, the cost of a thallium test is 261.22 dollars at our institution. Compared with those studies, we included more patients in our study. Moreover, we performed a propensity score analysis to control possible group differences in patients’ background conditions and minimize the effect of selection bias. We also analyzed the independent factors related to postoperative cardiac complications.
It is rational to consider that perioperative cardiac assessment could lead to safer surgery and fewer cardiac complications, as has been demonstrated in other specialties, such as thyroid and cardiovascular surgery [7, 8]. However, the results of previous studies did not indicate increased benefit in cases of geriatric hip trauma. Thus, we suppose that over-screening may happen in daily practice. Currently, during preoperative assessment by a cardiologist who follows the ACC/AHA guidelines, patients who have a functional capacity of < 4 METs require further evaluation, which is arbitrary and subjective, and may lead to over-diagnosis and incorrect indications of cardiac examinations. Vigoda et al.  performed a study of 548 anesthesiologist residents nationwide and examined their judgement in different scenarios. Fewer than half of the participants adhered to correct practice in accordance with standard care as set down in the 2007 ACC/AHA guidelines. We also assumed that the evolving minimally-invasive technique of hemiarthroplasty with a reduced surgical duration, in conjunction with postoperative early rehabilitation with mechanical/pharmaceutics thromboembolism prophylaxis, would result in a lower incidence of postoperative morbidity as compared with the same surgery decades ago. There may exist an imbalance between the expensive nuclear image test, which delays surgery for up to 4 days, and its clinical benefit.
A precisely selective coronary angiography and intervention are no doubt helpful to decrease postoperative morbidity/mortality. In our study, 113 patients underwent a thallium scan, but only 10 received coronary angiography and only 3 of the 10 patients who underwent angiography required interventions with a stenting procedure (2.65%). Thus, we identified a low rate of selective angiography with PCI after obtaining the results of a thallium scan, which may account for a decreased clinical benefit of testing. The thallium scan has a questionable negative predictive value in patients with "balanced ischemia", which was recognized by a condition of global myocardial ischemia. Several researchers discovered poor interpretation of a relative perfusion defect in affected segments, which is a common phenomenon in nuclear imaging [21–23].
There were several limitations of this study that should be considered. Most notably, there may be a selection bias, as dipyridamole-thallium scanning was ordered in high-risk patients who were likely inherently subject to a higher rate of 90-day cardiac complications. However, we attempted to balance the baseline patient condition and control for potential confounders. Second, the decision to utilize dipyridamole-thallium scanning was made by different cardiologists, and thus there may be some variation in the stratification and willingness to order additional cardiac tests. Third, we focused on 90-day morbidity and mortality, and thus did not account for any complications that may have occurred beyond that follow-up duration. It is necessary to discover a better cardiac assessment tool with better specificity that is less time-consuming and has a better negative predictive value. Currently, there is no consensus with regards to a thallium scan substitute but computed tomographic angiography (coronary CTA) has been noted to be useful. Huang et al.  investigated the value of coronary CTA in non-cardiac surgeries and found that this yielded improved perioperative risk stratification with a low rate of major cardiac events, high specificity, and good negative predictive value. The risk of a major cardiac event was 14% in patients with significant CTA findings . Future research involving prospective, randomized allocation of patients is warranted to minimize selection bias and group differences.