ORIGINAL ARTICLE _____________________________________________________________

Nonagenarians Undergoing CardiacSurgeryJohn P. Davis, M.D., Damien J. LaPar, M.D., M.Sc., Ivan K. Crosby, M.D.,John A. Kern, M.D., Christine L. Lau, M.D., Irving L. Kron, M.D.,and Gorav Ailawadi, M.D.

Department of Surgery, University of Virginia Health System, Charlottesville, Virginia

ABSTRACT Background: As life expectancy continues to rise and cardiac surgical outcomes improve, thenumber of nonagenarian (age>90 years) patients undergoing cardiac operations is increasing. However,little has been reported on cardiac surgical outcomes in this select patient population. The purpose of thisstudywas to examine current cardiac surgical outcomes for nonagenarian patients anddetermine the impactof extreme age on contemporary risk calculations. Study Design: From 2002 to 20012, 61,303 patientsunderwent cardiac operations as reported in a statewide Society of Thoracic Surgeons (STS) Adult CardiacSurgery database, including 108 nonagenarians. Patient and operative factors, including STS Predicted Riskof Mortality (PROM), were analyzed in order to compare to estimated risk measures. Results:Nonagenarianpatients (median age=92 years) had a high prevalence of preoperative cerebrovascular disease (23.1% [25/108]) and arrhythmia (55.6% [60/108]). Isolated coronary artery bypass grafting (CABG) (39.8% [43/108]) wasthemost commonoperation performedwithin this cohort, followed by aortic valve replacement (AVR: 35.2%[38/108], AVRRCABG23.1% [25/108]) operations. Overall nonagenarianmortalitywas 13% [14/108] andwasgreatest for AVR. Among nonagenarians with calculated STS PROM, observed to expected (O:E) ratios formortality ranged from 1.45 to 2.65 annually over the study period. Conclusions: Nonagenarian patientsrepresent a high-risk, elderly patient population with higher morbidity than predicted. Mortality is greatestfollowing aortic valve operations. These results suggest that current risk calculationsmay underestimate theimpact of extreme age on perioperative mortality. doi: 10.1111/jocs.12391 (J Card Surg 2014;29:600–604)

Life expectancy of the United States population isrising, and the percentage of the elderly individuals inthe population continues to increase. Recent populationestimates predict the number of individuals greaterthan 90 years of age to reach 8.7 million by the year2050.1,2 Additionally, the burden of cardiovasculardisease among nonagenarians continues to increase.3,4

Consequently, cardiac surgery in this population con-tinues to becomemore common in themodern surgicalera.5 While increasing reports of cardiac surgicaloutcomes have been published in the elderly, particu-larly in octogenarians, outcomes for nonagenarianpatients remain underreported. Available reports,however, remain limited to relatively small samplesizes and describe single-institution experiences, re-porting varying mortality and morbidity.6–14

Risk stratification of patients undergoing cardiacsurgery is fundamentally important for preoperativepatient counseling and tracking of outcomes. TheSociety of Thoracic Surgery (STS) Adult CardiacDatabase is commonly used in the United States inorder to assess and compare risk-adjusted outcomesfor patients undergoing cardiac surgery.15 The STSPredicted Risk of Mortality (PROM) has become anaccepted measure of estimated mortality risk, particu-larly for patients within the lowest deciles of risk.However, the STS risk models have demonstratedlimited performance to estimatemortality risk for selecthigh-risk patient populations.16 Therefore, the purposeof this study was to investigate outcomes within amulti-institutional cohort of nonagenarian patients andto assess the correlation between observed topredicted risk of mortality for this patient cohort.

METHODS

All cardiac operations were prospectively enteredinto the STS Adult Cardiac Surgery Database by 17different centers within the Commonwealth of Virginia,each participating in the Virginia Cardiac SurgeryQualityInitiative. We queried these data and reviewed all

Conflict of interest: The authors acknowledge no conflict of interest

in the submission.

Presented at the 99th Annual ACS Clinical Congress in Washington,

D.C. (October, 2013).

Address for correspondence: Gorav Ailawadi, M.D., Department of

Surgery, University of Virginia Health System, PO Box 800679,

Charlottesville, VA 22908. Fax: þ434-244-7588; e-mail: gorav@virginia.edu

600 © 2014 Wiley Periodicals, Inc.

patients who underwent cardiac surgery from 2002 to2012 (n¼61,303).We then further identified the subsetof nonagenarian patients (�90 years of age, n¼ 108).Because of the absence of patient identifiers incollected data and because the data were collectedfor reasons other than research, our analyses wereexempt from the University of Virginia InstitutionalReview Board, and participating institutions wereexempt from Health Insurance Portability and Account-ability Act consideration by the use of the SmallBusiness Agreement for Business Associates agree-ments between each hospital, participating surgeons,and the Virginia Cardiac Surgery Quality Initiative.

OUTCOMES

All study outcomes were established a priori beforedata analyses were initiated. The primary outcomes ofthis study were overall mortality and observed-to-expected ratios of the STS PROM and actual mortality.The secondary outcomes of interest were procedure-specific mortality, operative status, postoperativemorbidity, and hospital resource utilization.

STATISTICAL METHODS

Statistical analyses were utilized to test the nullhypotheses that clinical outcomes were not significant-

ly different as a function of nonagenarian status. Studyoutcomes and data comparisons were established apriori before data collection. Categorical variables areexpressed as group percentages. Continuous variablesare expressed as mean� standard deviation (SD) ormedian (25th, 75th percentile). Descriptive, univariatestatistics utilized either Pearson’s x2 or Fisher’s exacttest for categorical variables or independent, singlefactor analysis of variance (ANOVA) or the Mann-Whitney U test where appropriate. Calculated teststatistics were utilized to derive all two-tailed p-valueswith standard statistical significance of p< 0.05.

RESULTS

Patient and operative characteristics

From 2002 to 2012, a total of 108 nonagenarianpatients underwent cardiac surgery. Patient character-istics and operative characteristics for patients <90years and for those �90 years are listed in Table 1.Among nonagenarian patients, gender was relativelyevenly distributed, and the mean age was 92� 3 years.Themost common comorbidities included chronic renalinsufficiency (46.3%), cerebrovascular disease(23.1%), peripheral vascular disease (PVD) (17.6%),and diabetes mellitus (DM) (15.1%). Mean ejectionfraction (EF) was 55%. Compared to younger patients,

TABLE 1Patient and Operative Characteristics for All Patients Undergoing Cardiac Operations

Age �90% (n=108) Age <90% (n=61,195) P-Value

GenderMale 56.5% (61) 71% (43,473) <0.001Female 43.5% (47) 29% (17,722)Mean age (in years) 92�3 65�11

Comorbid diseaseCerebrovascular disease 23.1% (25) 13.9% (8512) <0.001Chronic lung disease 0.23Mild 14.8% (16) 10.1% (6181)Moderate 6.5% (7) 5.3% (3253)Severe 1.9% (2) 2.7% (1629)Diabetes 15.1% (17) 37.3% (22,839) <0.001Dyslipidemia 23.1% (25) 43.0% (26,291) <0.001Hypertension 75.0% (81) 78.9% (48,302) <0.001Peripheral vascular disease 17.6% (19) 13.6% (8340) <0.001Chronic renal insufficiency 46.3% (50) 3.6% (2179) 0.013Renal failure—dialysis 55.6% (60) 2.5% (1531) 0.02Arrhythmia 55.6% (60) 9.7% (5916) <0.001Congestive heart failure 13.0% (14) 1.9% (1138) <0.001Mean ejection fraction 55% 52%Left main disease >50% 20.4% (22) 24.9% (15,220) 0.004

Operation <0.001AV replacement 35.2% (38) 7.9% (4863)AV replacementþCABG 23.1% (25) 6.8% (4154)CABG only 39.8% (43) 79.5% (48,675)MV repair 0% (0) 1.3% (802)MV repairþCABG 0% (0) 0.9% (604)MV replacementþCABG 0% (0) 1.3% (778)MV replacement only 11.1% (2) 2.2% (1316)

Status 0.113Elective 56.5% (61) 48.2% (29,495)Urgent 41.7% (45) 48.4% (29,584)Emergent 1.9% (2) 3.3% (2014)

AV, aortic valve; CABG, coronary artery bypass graft; MV, mitral valve.

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nonagenarians, expectedly, presented with increasedpreoperative risk profiles (median STS PROM¼ 7.4� 6.2% vs. STS PROM¼1.4� 4.5%, p¼<0.001).

Among operative procedures, both CABG and aorticvalve replacement (AVR) were most common amongnonagenarians: 39.8% and 35.2%, respectively, whilecombined procedures and mitral operations were rare.Similarly, elective operations were performed in themajority of cases, and emergent operations wereperformed in 1.9% of cases. Isolated CABG wasmore common in the non-nonagenarian patient cohort(79.5%). AVR and AVRþCABGwere also less frequentamong non-nonagenarians (7.9% and 6.8% vs. 35.2%and 23.1%, p< 0.001).

Comparison of mortality, morbidity, and resourceutilization

Observed differences in mortality, morbidity, andhospital resource utilization for all patients are detailed inTable 2. Procedure-specific mortality can be seen inTable 3. Among postoperative complications, renalfailure (18.5%), prolonged mechanical ventilation(14.8%), and atrial fibrillation (30.6%) were mostcommon among nonagenarian patients and weremore common compared to younger patients. Operativemortality was 13% in the nonagenarian group compared

to 2.6% in younger patients (p¼<0.001). Similarly,nonagenarians accrued higher mean differences inintensive care unit (ICU) and total hospital length ofstay (LOS). With respect to operations, mortality washighest following AVR among nonagenarians, while thehighestmortality rate for younger patients occurred aftermitral valve replacement (MVR)þCABG.

Figure 1 illustrates biannual mortality and patientvolume relationships, and Figure 2 shows biannualobserved:expected (O:E) ratios. Operative volumesteadily increased over the study period,whilemortalitydecreased. Additionally, overall observed-to-expectedmortality (O:E ratio) generally decreased in the nonage-narian population over time. O:E ratioswere higher (>1)within the nonagenarian patient population in the earlierpart of the study. O:E ratios for the younger populationwere initially lower, but increased over time. There wasno significant difference between overall means of O:Eratios between groups (p¼0.97).

DISCUSSION

This study evaluates the clinical utility of expectedSTS risk scores for cardiac surgery in the nonagenarianpopulation. Overall, these data demonstrate that thenumber of operations performed on nonagenarianpatients is small, but increasing. Moreover, the STS

TABLE 2Postoperative Morbidity, Mortality, and Hospital Resource Utilization for All Patients Undergoing

Cardiac Operations

Complication Age �90% (n=108) Age <90% (n=61,195) P-Value

Renal failure 18.5% (20) 4.0% (2469) <0.001Renal failure—dialysis 3.7% (4) 1.6% (992) 0.001Stroke 3.7% (4) 1.5% (900) <0.001Prolonged ventilation 14.8% (16) 10.5% (6424) <0.001Pneumonia 7.4% (8) 3.2% (1973) <0.001Atrial fibrillation 30.6% (33) 18.7% (11,443) <0.001Cardiac arrest 5.6% (6) 1.6% (986) <0.001Perioperative MI 0.9% (1) 0.2% (137) 0.003Reoperation for bleeding 2.8% (3) 2.2% (1328) <0.001Sternal wound infection 0.9% (1) 0.4% (257) 0.004Septicemia 3.7% (4) 1.0% (609) <0.001ICU LOS (mean in days) 5.2�6.7 3.3�6.0Hospital LOS (mean in days) 11�10 7�8Readmission within 30 days 8.3% (9) 8.3% (5082) 0.001Mortality 13% (14) 2.6% (1594) <0.001

MI, myocardial infarction; ICU, intensive care unit; LOS, length of stay.

TABLE 3Operation Specific Mortality for All Patients Undergoing Cardiac Operations

Operation-Specific Mortality Age �90% (n=108) Age <90% (n=61,195) P-Value

AV replacement 18.4% (7) 3.2% (1.958) <0.001AV replacementþCABG 12% (3) 5% (3060) <0.001CABG only 4% (9.3) 2.1% (1845) <0.001MV repair 0% (0) 1.5% (918) <0.001MV repairþCABG 0% (0) 7.0% (4284) <0.001MV replacementþCABG 0% (0) 10.1% (6303) <0.001MV replacement only 0% (0) 6.0% (3872) <0.001

AV, aortic valve; CABG, coronary artery bypass graft; MV, mitral valve.

602 DAVIS, ET AL. J CARD SURGNONAGENARIANS UNDERGOING CARDIAC SURGERY 2014;29:600–604

PROM score does not always correlate with observedmortality and morbidity after cardiac surgery amongnonagenarian patient populations, but has improvedover time.

Our mortality rate of 13% fell within the previouslydocumented mortality range of 5% to 20%.5,7–12,14

Despite statistically significant differences betweenboth patient populations when comparing preoperativepatient characteristics, the nonagenarian populationdisplayed a higher incidence of cerebrovascular dis-ease, and renal failure, but lower incidences of DM,hypertension, and left main coronary artery disease.Although variable fromstudy to study, there is a trend oflower incidence of comorbid disease among thenonagenarian population, which may suggest thesepatients must be reasonably healthy to live 90 years ofage. CABGþValve procedures have typically exhibitedthe highest mortality rate in prior nonagenarianseries9,10,13; however, solitary AV replacement wasassociated with the highest operative mortality in thenonagenarian cohort. The incidence of arrhythmias andprolonged ventilation observed in our patients wasrelatively consistent with prior series, and the observedICU LOS of 5.2� 6.7 days and a hospital LOS of 11� 10days appeared to bewellwithin the ranges of previouslypublished series as well.7–9,11–14 Easo and colleaguescalculated the STS risk score for a group of 17nonagenarians, which resulted in a risk score of26.1�16.5%.11 This figure was much higher than our

median score of 7.4� 6.2%. To our knowledge, noother studies directly calculated the STS PROMnorO:Eratios for nonagenarians undergoing cardiac surgery.

The STS database has been compared to othercommonly implemented cardiac surgery risk stratifica-tion tools and performs well for a large majority ofpatient populations,16–19 but these indices have alsobeen shown to underpredict mortality in populationsthat are above the lowest decile of risk.16,18 Thesefindings in previously reported series are similar tothose in the current series as the STS PROMconsistently underpredicted observed mortality, result-ing in surprisingly elevated O:E ratios. Interestingly, theO:E ratios for the elderly population were not signifi-cantly different from the ratios for those under the ageof 90. Additionally, the trend of volume of nonagenar-ians undergoing cardiac surgery in our population isincreasing annually. These observations are encourag-ing as this suggests that cardiac surgery outcomes inthe nonagenarian population are improving as operativevolume increases and theSTSPROM is not significantlydifferent than in the younger patient population.

Despite the numerous variables taken into consider-ation with the STS risk calculator, mortality in the elderlypopulation was often underpredicted in the earlierportion of the study period. Researchers and clinicianshave proposed means to improve these predictions inthe elderly population, and the addition of a frailty ordisability factor to the scoring system has shownpotential for more accurately predicting mortality inthese patients. Sundermann et al.20 implemented acomprehensive assessment of frailty that included amultitude of functional and physiologic variables. Theaddition of comprehensive assessment of frailty to theSTS score revealed a significant correlation to theprediction of 30-day mortality. Furthermore, Afilaloet al. evaluated multiple frailty and disability metrics,and their relationship to the accuracy of multiple cardiacsurgery risk calculators. The addition of select frailty anddisability metrics to the STS PROMM was shown toallow for amore accurate prediction of poor outcomes inelderly patients.17 These findings ultimately resulted inthe addition of a 5-mgait speed to the STS risk calculator.

This study has limitations. One limitation is itsretrospective design, which introduces inherent selec-tion bias, as only the healthiest nonagenarianswould beselected for an operation. The constraints of STSdefinitions and de-identified data points are a limitation,and it is possible that specific variables may not becaptured consistently from patient to patient. The smallsample size of nonagenarian patients limits the study.There is also a lack of long-term follow-up in the VCSQIdatabase.

In conclusion, we believe that the presenteddata reinforce the commonly accepted notion thatnonagenarian patients undergoing cardiac surgery cer-tainly represent a high-risk population with highermortality and morbidity than their younger counterparts.As the number of nonagenarians undergoing cardiacsurgery continues to increase, further efforts to refineour ability to predict postoperative morbidity, mortality,and resource utilization will not only enhance patient

Figure 2. Trend in biannually averaged observed-to-expectedmortality (O:E ratio) for nonagenarian patients and patientsunder the age of 90 years undergoing cardiac operations duringthe study period. Comparisons of means between the twogroups do not reach significance (p¼0.097).

Figure 1. Overall trends in operative volume and mortality fornonagenarian patients undergoing cardiac surgery (n¼108).

J CARD SURG DAVIS, ET AL. 6032014;29:600–604 NONAGENARIANS UNDERGOING CARDIAC SURGERY

outcomes, but improve the delivery of quality surgicalcare with appropriate expectations.

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