key: cord-1037345-2af8l58a
authors: Nguyen, Tom C.; Thourani, Vinod H.; Nissen, Alexander P.; Habib, Robert H.; Dearani, Joseph A.; Ropski, Allan; Crestanello, Juan A.; Shahian, David M.; Jacobs, Jeffrey P.; Badhwar, Vinay
title: The Effect of COVID-19 on Adult Cardiac Surgery in the United States in 717,103 Patients
date: 2021-07-31
journal: Ann Thorac Surg
DOI: 10.1016/j.athoracsur.2021.07.015
sha: 3207aa7a15e4e98d0f092517d67753fe18bebb5a
doc_id: 1037345
cord_uid: 2af8l58a

Background COVID-19 has changed the world as we know it, and the United States continues to accumulate the largest number of COVID-related deaths worldwide. There exists a paucity of data regarding the effect of COVID-19 on adult cardiac surgery trends and outcomes on regional and national levels. Methods The STS Adult Cardiac Surgery Database was queried from January 1, 2018 to June 30, 2020. The Johns Hopkins COVID-19 database was queried from February 1, 2020 to January 1, 2021. Surgical and COVID-19 volumes, trends, and outcomes were analyzed on a national and regional level. Observed-to-expected ratios were used to analyze risk-adjustable mortality. Results 717,103 adult cardiac surgery patients and over 20 million COVID-19 patients were analyzed. Nationally, there was 52.7% reduction in adult cardiac surgery volume, and 65.5% reduction in elective cases. The Mid-Atlantic region was most affected by the first COVID-19 surge, with 69.7% reduction in overall case volume and 80.0% reduction in elective cases. In the Mid-Atlantic and New England regions, the observed-to-expected mortality for isolated coronary bypass increased as much as 1.48 times (148% increase) pre-COVID rates. After the first COVID-19 surge, nationwide cardiac surgical case volumes did not return to baseline, indicating a COVID-19-associated deficit of cardiac surgery patients. Conclusions This is the largest analysis of COVID-19 related impact on adult cardiac surgery volume, trends, and outcomes. During the pandemic, cardiac surgery volume suffered dramatically, particularly in the Mid-Atlantic and New England regions during the first COVID-19 surge, with a concurrent increase in observed-to-expected 30-day mortality.

Coronavirus disease , caused by the severe acute respiratory syndrome coronavirus (SARS-CoV)-2, is a highly infectious disease thought to have emerged from Wuhan China in 2019. [1] On March 11 th , 2020 COVID-19 was recognized by the World Health Organization (WHO) as a global pandemic, and as of January 2021, the United States (US) has had more reported cases than any other nation. [2] Despite shelter-in-place and physical distancing mandates, hospitals were initially overwhelmed with a massive influx of COVID-19 patients, requiring dramatic changes to resource allocation, redeployment of staff, operative volumes, and infection mitigation strategies. [3, 4] Despite improvements in our understanding of COVID-19 pathophysiology and the utility of early steroids, remdesivir, and/or mechanical circulatory support, many questions remain unanswered. [5] [6] [7] [8] [9] Previous reports have demonstrated significant morbidity and mortality risk for patients requiring elective or emergent surgery who are diagnosed with COVID-19, regardless of pre-or postoperative COVID-19

contraction. [10] Thoracic surgery patients represented a minority of this previously-reported cohort, and data specific to adult cardiac surgery patients with COVID-19 are limited to case series, with a relative paucity of larger scale reports. [11] [12] [13] Utilizing the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (ACSD), our goals are to better understand the impact of COVID-19 on adult cardiac surgery volumes, trends, and the influence of the COVID-19 surge on risk-adjusted mortality on a national and regional scale.

Patient Population: Using the STS ACSD, we examined patients undergoing cardiac operations from 01 January 2018 -30 June 2020. Cardiac surgery patients were grouped into Pre-COVID, Early-COVID, and COVID Storm groups to examine demographic differences, while highlighting potentially unique factors among those operated on during the first COVID-19 case surge. When examining overall surgical volume trends, all operations were considered, with additional stratified reporting based on case status as elective or non-elective (urgent, emergent, or emergent salvage cases). As defined by the STS, urgent procedures represent those required during the same hospitalization to prevent further clinical J o u r n a l P r e -p r o o f deterioration, emergent procedures involve patients with refractory or ongoing cardiac compromise not responsive to any therapy other than cardiac surgery, and emergent salvage procedures include patients undergoing cardiopulmonary resuscitation (CPR) or extracorporeal membrane oxygenation (ECMO) to sustain life. [14] Patients undergoing procedures at STS reporting sites outside the United States were excluded. Preoperative variables and postoperative outcome definitions included those provided by the STS as previously defined.

[14] Our primary research goals were to examine adult cardiac surgery temporal volume trends before, during and after the first COVID-19 peak on national and regional levels, as well as to examine any association of COVID-19 surges on short-term mortality both nationally, and in regions that were disproportionately affected by COVID-19. [15] Cardiac surgical volume trends were analyzed based on monthly volume, and COVID-19 cases were ascertained in weekly volumes to allow sufficient granularity for analysis and reporting. When calculating observed-to-expected mortality ratios, only operations with STS risk models were considered: (1) isolated coronary artery bypass grafting (CABG), (2) isolated aortic valve replacement (AVR), (3) isolated mitral valve replacement (MVR), (4) AVR+CABG, (5) MVR+CABG, (6) isolated mitral valve repair (MV repair), and (7) MV repair+CABG. Risk-adjusted mortality is reported for the above procedures, as previously described. [16, 17] Table 1 lists demographic and preoperative characteristics of our study cohort. Using the nine STS regions, regional contributions to the overall study cohort are shown in Figure 1 Figure 4 . Any regional deviation above the national COVID-19 case rate represents a regional surge compared to the national COVID-19 case rate at a given time.

Regional Cardiac Surgery Volume Trends: Regional cardiac surgery case volumes during the first COVID-19 surge were compared to mean regional case volumes of the respective months in previous years, as plotted in Figure 5 , demonstrating the greatest reduction in regional surgical case volumes in the Mid-Atlantic and New England regions. Given that the Mid-Atlantic region was impacted with both the highest number of COVID-19 cases during the first surge in the United States, as well as the greatest relative reduction in cardiac surgical case volumes, this region was chosen for a regional subgroup analysis of cardiac volume trends during the early COVID-19 pandemic. 

The COVID-19 pandemic continues to represent an unprecedented global health challenge, as we continue to confront issues related to healthcare resources, personnel, and methods for safe delivery of care under new circumstances. We report the largest and most comprehensive description of the impact of the COVID-19 pandemic on cardiac surgical volumes, trends, and outcomes on a regional and national scale. This effort is unique because, unlike many other surgical databases, the STS ACSD captures more than 98% of all adult cardiac surgery cases in the United States based on the most recent analyses.

After examination of nearly three-quarters of a million adult cardiac surgical cases and more than 20 million COVID-19 cases, a clear nadir of cardiac surgical volumes was seen in April 2020, with reductions to less than half of the previous level, notably including a nearly 40% reduction in all nonelective cases. When focused temporally on the first nationwide COVID-19 surge in the spring of 2020, cardiac case volumes in the Mid-Atlantic and New England regions were affected to the greatest degree, with an even greater reduction in non-elective cases by nearly 60% in the Mid-Atlantic.

However, when examining cardiac surgical volumes after April 2020, though some volume recovery is seen, there was not a rebound of case volumes to above-baseline levels that would adequately account for the previous non-elective cardiac surgical case deficit, either regionally nor nationally. This finding suggests a COVID-19 related deficit of untreated adult cardiac surgery patients.

The consequence of these untreated patients remains unclear. As described above, the STS defines even the healthiest of this subset of patients as "urgent", requiring cardiac surgery during the same hospitalization to prevent further deterioration. There are several possible explanations for the absence of a sufficient rebound in non-elective cases. First, some patients who were potential candidates for either cardiac surgery or less invasive procedures may have been directed towards less-invasive alternatives, favoring shorter hospitalization and less resource utilization ( e.g., percutaneous coronary intervention

[PCI] rather than CABG, or transcatheter aortic valve implantation [TAVI] rather than AVR). However, data from other hotspot regions actually suggest a concomitant reduction in overall and relative PCI rates during the early COVID-19 surge, which does not support this explanation. [18] While low-risk TAVI approval may have contributed slightly to a decline in patient referral for surgical AVR during the pandemic, it is again unlikely that this factor alone would account for such a dramatic nadir in operative volume. Second, patients for whom elective vs. urgent status is unclear or borderline in the estimation of the heart team may be recategorized as elective and followed closely as outpatients until an appropriate surgical date can be arranged based on local COVID-19 rates. Attrition rates while awaiting various cardiac procedures have been previously examined, demonstrating approximately 2-11% for CABG at one month, and approximately 4% for AVR at one month. [19, 20] These rates remain concerning, and J o u r n a l P r e -p r o o f may account for some loss of patients whose previously non-elective surgery was deferred, though the exact proportion of such cases remains unclear. Third, patients may be reluctant to seek appropriate inhospital care at all in the midst of a pandemic because they fear contracting COVID-19, or further overwhelming their local healthcare system. Although this mechanism is difficult to quantify nationally, it is supported by the growing number of late-presenting complications of myocardial infarction and other acute cardiac diseases which timely, invasive therapies may have mitigated. [21] [22] [23] This final consideration is strengthened, and is especially concerning, because of reportedly increased rates of latepresenting ST-elevation myocardial infarctions and associated mechanical complications during the pandemic which are independent of local COVID-19 case volumes. [24] Collectively, these various mechanisms may account for some lack of a rebound in surgical case volumes after April 2020. However, the inability to clearly account for these patients, particularly the large number of non-elective cases, remains highly concerning for a COVID-19 related patient deficit. further examination, and they may be related to the cardiac case volume reductions at regional and local levels. Although 'statistically significant' differences are shown in cardiac surgery patient baseline characteristics before and ruing the COVID-19 pandemic, this is primarily related to the large overall population studied, while the absolute numerical differences between groups remain relatively minimal J o u r n a l P r e -p r o o f (Table 1) . Potential mechanisms include hospital resources and manpower issues including urgent reallocation of hospital bedspace, resources, and cross-deployment of physician and physician personnel, as well as separate state and local governmental mandates to cease all elective surgical cases to prevent overwhelming local healthcare systems. In the Mid-Atlantic and New England regions, where peak case reductions and increased COVID-19 case volumes occurred simultaneously, the O:E mortality ratio increased sharply, unlike other regions, where cardiac case volume reductions preceded regional peaks in COVID-19 cases. This suggests that the reason for cardiac case decreases in the Mid-Atlantic and New-England regions may have been more influenced by hospital resources, manpower, and reallocation, without sufficient lead time to necessarily reduce case volumes in a planned manner to preserve these resources. Conversely, after a reduction in operative volumes in April 2020, other regions showed subsequent increased cardiac surgical cases towards baseline levels, even during months when regional COVID-19 cases were rising, suggesting that the first nadir in cases may have been driven by implementation of forced prophylactic surgical case reductions, rather than being faced with unanticipated resource scarcity. We may speculate that this contributed, at least partially, to the increased O:E mortality ratio uniquely in the Mid-Atlantic and New England regions during the first COVID-19

surge, compared to other regions.

In addition to resource and manpower scarcity, other factors may account for the COVID-19 effect on short-term mortality in the Mid-Atlantic and New England regions. These dramatic O:E shifts are completely idiosyncratic, especially as these regions were collectively performing better than expected (O:E mortality ratios well below 1) in the pre-COVID-19 era. Additional, potential mechanisms include the risk of perioperative COVID-19 infection in these hotspot regions, physician and nonphysician provider fatigue, and selection of higher risk patients in a manner that is not completely characterized by the current STS risk models for the risk-adjustable procedures being reported.

Based on the above findings, as well as the breadth and depth of data captured by the STS ACSD, we plan future research to specifically focus on many of the unresolved issues described in this manuscript. Additional data regarding individual patient COVID-19 status, unique perioperative risk J o u r n a l P r e -p r o o f factors for morbidity and mortality, and specific rates of complications (e.g., tracheostomy, bleeding, need for postoperative ECMO, early valve-related thrombotic complications) will contribute substantially to these ongoing analyses. As we continue to face this pandemic, continued collaboration, use of datasets such as the STS ACSD, and database linkages will be critical to answer these important questions.

Limitations: Our manuscript has several limitations, including the lack of granularity regarding the exact reason(s) for the effect of COVID-19 on O:E mortality ratios in regions most affected by the first COVID-19 peak. We also lack individual patient COVID-19 infection status, which through database linkages will enhance future analyses. Finally, our analysis is primarily focused on the first COVID-19 surge in the United States, though it is our hope that other countries will learn from these early experiences.

We present the largest description of the impact of COVID-19 on national and regional cardiac surgical case volumes, trends, and outcomes. We have quantified dramatic cardiac case volume reductions nationwide, further magnified in hotspot regions during the first COVID-19 case surge in the United States. These findings were accompanied by dramatic increases in mortality O:E even in regions that previously performed at better-than-expected levels. The reasons for case volume reductions are multiple, vary by region, and may partially explain the source of regional increases in 30-day mortality

Notably, a rebound of case volumes to account for previous reductions in non-elective cases has yet to be seen. This COVID-19 related cardiac surgical case deficit, particularly among non-elective cases, remains concerning, as delaying or avoiding appropriate cardiac surgical care may lead to unnecessary morbidity and mortality, regardless of infection status. We plan further research to address these issues.

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