key: cord-257684-4b66lenw authors: Salenger, Rawn; Etchill, Eric W.; Ad, Niv; Matthew, Thomas; Alejo, Diane; Whitman, Glenn; Lawton, Jennifer S.; Lau, Christine L.; Gammie, Charles F.; Gammie, James S. title: The Surge after the Surge: Cardiac Surgery post-COVID-19 date: 2020-05-04 journal: Ann Thorac Surg DOI: 10.1016/j.athoracsur.2020.04.018 sha: doc_id: 257684 cord_uid: 4b66lenw ABSTRACT Background The COVID-19 pandemic has dramatically reduced adult cardiac surgery case volumes as institutions and surgeons curtail non-urgent operations. There will be a progressive increase in deferred cases during the pandemic that will require completion within a limited time frame once restrictions ease. We investigated the impact of various levels of increased post-pandemic hospital operating capacity on the time to clear the backlog of deferred cases. Methods We collected data from four cardiac surgery programs across two health systems. We recorded case rates at baseline and during the COVID-19 pandemic. We created a mathematical model to quantify the cumulative surgical backlog based on the projected pandemic duration. We then used our model to predict the time required to clear the backlog depending on the level of increased operating capacity. Results Cardiac surgery volumes fell to 54% of baseline after restrictions were implemented. Assuming a service restoration date of either June 1 or July 1, we calculated the need to perform 216% or 263% of monthly baseline volume, respectively, to clear the backlog in one month. The actual duration required to clear the backlog is highly dependent on hospital capacity in the post-COVID time period, and ranges from one to eight months depending on when services are restored and degree of increased capacity. Conclusions Cardiac surgical operating capacity during the COVID-19 recovery period will have a dramatic impact on the time to clear the deferred cases backlog. Inadequate operating capacity may cause substantial delays and increase morbidity and mortality. If only pre-pandemic capacity is available, the backlog will never clear. Background. The COVID-19 pandemic has dramatically reduced adult cardiac surgery case volumes as institutions and surgeons curtail non-urgent operations. There will be a progressive increase in deferred cases during the pandemic that will require completion within a limited time frame once restrictions ease. We investigated the impact of various levels of increased postpandemic hospital operating capacity on the time to clear the backlog of deferred cases. We collected data from four cardiac surgery programs across two health systems. We recorded case rates at baseline and during the COVID-19 pandemic. We created a mathematical model to quantify the cumulative surgical backlog based on the projected pandemic duration. We then used our model to predict the time required to clear the backlog depending on the level of increased operating capacity. Results. Cardiac surgery volumes fell to 54% of baseline after restrictions were implemented. Assuming a service restoration date of either June 1 or July 1, we calculated the need to perform 216% or 263% of monthly baseline volume, respectively, to clear the backlog in one month. The actual duration required to clear the backlog is highly dependent on hospital capacity in the post-COVID time period, and ranges from one to eight months depending on when services are restored and degree of increased capacity. Cardiac surgical operating capacity during the COVID-19 recovery period will have a dramatic impact on the time to clear the deferred cases backlog. Inadequate operating capacity may cause substantial delays and increase morbidity and mortality. If only prepandemic capacity is available, the backlog will never clear. Key words: cardiac surgery; COVID-19; surgical capacity; coronary artery bypass grafting The COVID-19 pandemic has resulted in dramatically lower adult cardiac surgery case volumes, as institutions and surgeons are following state and federal guidelines to curtail non-urgent operations. There will be a progressive increase in deferred cases during the pandemic that will require completion within a limited time frame once pandemic restrictions ease, in order to avoid excess morbidity and mortality [1] [2] [3] . By definition, programs will have to achieve higher daily case rates than prior to the pandemic in order to service the excess demand. The postpandemic surge in adult cardiac surgery could overwhelm current hospital resources without proper planning. Data were collected from four institutions across two health systems. Each system included two large academic centers and two affiliated community cardiac surgery programs. First, we calculated a combined baseline case rate across centers, pre-pandemic, by quantifying all cases done from January 2019 to February 29, 2020. Inclusion criteria included any adult cardiac surgery case being performed in the operating room with a cardiac surgeon as primary or co-surgeon. Heart and lung transplant, ventricular assist device, and transcatheter aortic and mitral valve replacements were included. Primary extracorporeal membrane oxygenation (ECMO) cases and pediatric cases were excluded. Next, we calculated the combined rate of cases during the early part of the pandemic. Raw data was collected from March 16 th through April 12 th and this was used to extrapolate a new "pandemic" surgical case rate. March 16 th was the day after the state of emergency was declared in the State of Maryland. We calculated the number of patients that would have surgery deferred during the pandemic, and the length of time necessary to service the backlog in a timely fashion once restrictions were lifted. Mathematical models were used to investigate the impact of the date that restrictions are lifted, and variable levels of hospital operating capacity on the time that would be required to address the backlog. To calculate the current backlog (B) on any given day (T), we developed the equation B = (R 0 -R p ) (T -T 0 ). This is the difference in the daily case rates multiplied by the number of days that difference had existed. T1 was then defined as the day that restrictions were eased and full operating capacity regained. Next, the number of operating days necessary to perform all the backlogged cases, defined as backlog time (BT), was calculated. The model was designed to predict the length of time required to clear the backlog based on the amount of extra operating capacity a hospital could achieve. Our prediction model defined T 0 as the day the pandemic began, and T 1 as the day restrictions were lifted. Each hospital's post-pandemic daily case rate would be defined by an acceleration factor (a) multiplied by the original prepandemic case rate, R 0 . The time required to clear the backlog of cases, BT, was then calculated. BT was defined by the equation BT = (1 -R p /R 0 ) (T1 -T0) / (a-1). The acceleration factor (a) represented how much surgical throughput a program could achieve above baseline. This factor would have to be greater than 1 in order to incorporate some amount of deferred cases into the operating schedule in addition to baseline cases. Cases were initially curtailed in early to mid-March 2020 and then more drastically in April as recommendations to postpone all but emergency operations became stronger. Baseline total case rate for the four combined programs was 306 adult cardiac surgery cases per month. During the pandemic that rate initially fell to 234, then to 164 cases per month once full restrictions were implemented (54% of normal). During this time the number of deferred cases would be estimated to grow to 356 by June 1 and 498 by July 1. This represents 216% to 263% of normal average monthly volume depending on the duration of the pandemic (Figure 1 ). The daily case rates were also calculated. We assumed 20 operative weekdays per month. For the combined health systems, the average daily case rate pre-pandemic, defined as R 0 , was 15.3. The daily case rate during the pandemic, defined as R p , was calculated to be 8.2 (Table 1) . We also calculated the baseline and pandemic daily case rates for three broad categories of cases including coronary artery bypass grafting (CABG), open valve surgery, and transcatheter aortic and mitral valve replacements (TAVR/TMVR) (Figure 1 ). Combined CABG/valve cases were counted as CABG because we felt that the patient's coronary disease would often dictate more urgent triage (Figure 2 ). Isolated valve cases were more likely to be deferred than patients with isolated or concomitant coronary disease. Transcatheter cases were treated differently between the health systems. One system's transcatheter case rate fell from 34 per month to 8 cases per month, while the other system increased their transcatheter cases from 21 per month to 32 cases per month. This equated to approximately a 75% decrease in one system's transcatheter cases and a 30% increase within the neighboring system. This differential treatment of transcatheter cases partially mitigated the overall backlog accumulation. CABG cases and valves were triaged similarly by the health systems and these case rates fell by 50% and 71% respectively. Next, we used our mathematical model to predict the number of cardiac surgery cases deferred during the pandemic, and the length of time required to operate on the backlog, dependent on the amount of increased operating capacity institutions could achieve. Time to clear the backlog, BT, was calculated using our mathematical model (Figure 3 ). This was considered for the possibility of restored services on June 1 or July 1 with varied levels of case capacity (Figure 4 ). Assuming services were restored June 1, the backlog could be cleared between 1-6 months, depending on degree of increased capacity. If services resumed July 1, the cardiac surgery backlog would be estimated to take between 2-8 months to clear according to the increased capacity achieved. Progressively increasing the operating capacity had a dramatic effect on reducing the time to clear the backlog. If capacity is not increased above baseline (acceleration factor = 1.0), the backlog will never be cleared. In response to the Covid-19 pandemic, adult cardiac surgery programs have dramatically curtailed operating activity, limiting cases to urgent and life-threatening emergencies. This slowdown has resulted in a growing backlog of adult cardiac surgery cases which will require surgical therapy in a finite time frame to improve quality of life and survival. Our study analyzed the deliberate deceleration in adult cardiac surgery cases that has occurred at the two busiest cardiac surgical programs in the state of Maryland in response to the COVID 19 pandemic. We observed a 54% drop in cardiac surgical volume, and subsequently a backlog that would require a monthly operating volume of 216% to 263% of baseline. Since this would be challenging to accomplish in one month, we predicted that the amount of time necessary to clear the backlog would range from 1 to 8 months based on varied estimates of post-pandemic increased operational capacity. Our data further suggest that deferred cardiac patients were triaged differently during the pandemic and that the composition of the waiting list is directly related to the triaging mechanism. As expected, isolated valve patients were preferentially deferred compared to patients with any coronary artery disease. We were surprised to see the differences in transcatheter case triage between the two systems. One system deferred the majority of transcatheter cases, while the other increased their rate, mainly TAVR cases. Although our data did not include reasons for triage decisions, this may have been due to differing thresholds for observing patients with severe aortic stenosis and uncertainty regarding best practice when deferring cardiac services. Others have attempted to characterize the needs for surgical services after natural disasters by establishing a baseline surgical rate and then examining the incidence of injury during a disaster [4] . A study of the Nepal earthquakes in 2015 demonstrated an acute need for surgical therapy that was more than double the annual Nepalese operating capacity, highlighting the need to be able to increase surgical capacity at critical times. Another study focused on the aftermath of Hurricane Charley and found a thirty-two percent increase in adverse medical outcomes for patients with chronic medical conditions related to both increased demand and shortfalls in care delivery [5] . Similar to our investigation, these studies focused on increased healthcare demand following unpredictable events. Our analysis differed because we analyzed the effect of an unexpected viral pandemic that necessitated a nearly 50% decline in surgical volume followed by an anticipated surge in surgical demand. Our study is novel in that we prospectively attempted to predict system capacity needs in order to service the anticipated surgical surge. This will require local hospitals and health systems to examine capacity, set priorities, and plan for adequate hospital capacity to service the backlog of cardiovascular patients [6, 7] . The global cardiac surgery response post-COVID will be complicated by prior exhaustion of hospital supplies and human resources from the pandemic, and competition for resources and operating room availability with other surgical and medical subspecialties, which will also have backlogs. The recently published joint statement from the American College of Surgeons and others provides guidance on when to safely reopen operating room capacity and includes recommendations for testing, personal protective equipment, and case prioritization [8] . We believe that it will be important to maintain an incident command approach during the late phases of the COVID epidemic as we transition to re-establishing, and increasing, our prepandemic workflow. Planning should begin now, and crucially, prioritize patients with significant risks arising from delayed operations. The risks of deferring needed cardiac treatment have been previously demonstrated. Reported mortality rate while waiting for surgical or transcatheter aortic valve replacement can be as high as 3.7% at one month and 11.6% at six months [2] . For patients awaiting coronary surgery, median waiting list mortality rates of 2.6% per month have been reported with mortality risk increasing 11% per month. Additionally, 12% of patients experienced a myocardial infarction while on the waiting list [1, 3] . We have attempted to estimate the resources required in planning for the post-pandemic surge in adult cardiac surgical volume. The capacity estimates for a given health system would depend on the percent increase in productivity targeted post pandemic. By utilizing our mathematical model, a health system could predict the time required for servicing their surgical backlog and adjust operating capacity accordingly. Actualizing a plan to increase capacity may occur gradually and this will further increase waiting time for deferred patients. Increasing capacity will also require proportional adjustments in resources such as operating rooms, ICU and telemetry beds, and provider staff. For the majority of hospitals, OR time is the most expensive resource. Consequently, increasing ICU and telemetry capacity to avoid operating room holds and cancellations is likely the most cost-effective approach to achieving increased throughput. The number of additional beds, nurses, and advanced practice providers needed can be calculated based on baseline resources. Maximizing efficiency through early telemetry discharge, decreasing intensive care length of stay, level loading elective cases in the OR, temporarily altering staffing models, and staggering cases can help increase throughput capacity [9, 10] . Another possible solution is to temporarily relocate some non-cardiac surgical cases to other facilities within a health system. In fact, maintaining the incident command center set up by many hospitals and utilizing some of the same workforce and bed solutions employed during the pandemic may be of value in delivering critical cardiac services in a timely fashion. Our analysis has several limitations. Firstly, we have assumed that historical rates of surgery will accurately predict future rates. This may be incorrect for several reasons. During the pandemic patients may be treated with alternative medical and interventional therapy, obviating the need for surgery. Patients treated medically with symptomatic relief may decide not to pursue more aggressive treatment. Other patients may be reluctant to incur out of pocket costs during this time of financial difficulty. Additionally, there will unfortunately be some degree of attrition of patients from cardiovascular and COVID-related mortality. The pent up demand could also accrue more slowly than calculated. Cardiac surgeons sit at the bottom of a virtual funnel which begins with patients seeking medical care, referral to a cardiologist, diagnostic testing, and finally evaluation for surgery. Each step along this pathway will be delayed during, and likely for some time after, the pandemic. Delays would function as a governor on the acceleration of post-pandemic cardiac surgical demand. Our study does, however, provide concerning data delineating a large group of patients with surgical level cardiovascular disease whose treatment has been necessarily deferred. Our hope is that our modeling can be used to calculate the productivity increase necessary to treat patients in an acceptable time frame. Further study could help better define the overall effects of a pandemic on the care of cardiovascular patients. Although challenging and costly, early post-pandemic operating capacity will need to be greater than the original daily capacity to satisfy the pent-up surgical demand. Not planning for post pandemic volume could result in a second wave of non-COVID cardiovascular mortality. 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