Treadmill Stress Test Research Articles

Correlation between Wall Motion Score Index (WMSI) and Anatomical M-mode (AAM) Systolic Thickening with Functional Capacity in Heart Failure among Post-myocardial Infarction Patients

Exercise capacity among cardiac patients is not sufficiently predicted using left ventricular ejection fraction resting measurement. The echocardiographic measurement using Wall Motion Score Index (WMSI) and Anatomical M-mode (AAM) Systolic Thickening post-myocardial infarction was studied to determine its correlation with functional capacity. We conducted a cross-sectional study of 33 consecutive post-MI patients. The inclusion criteria included heart failure patients with NYHA class I-II visiting the cardiology outpatient clinic of Soetomo Hospital, Surabaya. A resting echocardiogram, measuring WSMI and AMM systolic thickening of basal and mid-LV segments, was taken. The patients underwent a treadmill stress test using the Naughton protocol on the same day of their echocardiography examination. Samples were then analyzed using SPSS 2.0. Study subjects were 69.7% males with age 58.45±6.2 years old and BMI 24.07±3.2 kg/m2. The proportion of hypertension was 60.6%, smoking 51.5%, diabetes mellitus 42.4%, and dyslipidemia 42.4%. WMSI was 1.68±0.45, mean AMM systolic thickening 39±13%, and exercise capacity 3.69±1.8 METs. There was a moderate negative correlation of WMSI and a moderate positive correlation of AMM systolic thickening with functional capacity (r = –0.466, r = 0.415 consecutively; p<0.05). WMSI and AMM systolic thickening were correlated with functional capacity in post-MI patients with heart failure.

Association of BMI, Fitness, and Mortality in Patients With Diabetes: Evaluating the Obesity Paradox in the Henry Ford Exercise Testing Project (FIT Project) Cohort

To determine the effect of fitness on the association between BMI and mortality among patients with diabetes. We identified 8,528 patients with diabetes (self-report, medication use, or electronic medical record diagnosis) from the Henry Ford Exercise Testing Project (FIT Project). Patients with a BMI <18.5 kg/m2 or cancer were excluded. Fitness was measured as the METs achieved during a physician-referred treadmill stress test and categorized as low (<6), moderate (6-9.9), or high (≥10). Adjusted hazard ratios for mortality were calculated using standard BMI (kilograms per meter squared) cutoffs of normal (18.5-24.9), overweight (25-29.9), and obese (≥30). Adjusted splines centered at 22.5 kg/m2 were used to examine BMI as a continuous variable. Patients had a mean age of 58 ± 11 years (49% women) with 1,319 deaths over a mean follow-up of 10.0 ± 4.1 years. Overall, obese patients had a 30% lower mortality hazard (P < 0.001) compared with normal-weight patients. In adjusted spline modeling, higher BMI as a continuous variable was predominantly associated with a lower mortality risk in the lowest fitness group and among patients with moderate fitness and BMI ≥30 kg/m2. Compared with the lowest fitness group, patients with higher fitness had an ∼50% (6-9.9 METs) and 70% (≥10 METs) lower mortality hazard regardless of BMI (P < 0.001). Among patients with diabetes, the obesity paradox was less pronounced for patients with the highest fitness level, and these patients also had the lowest risk of mortality.

Clinical Profile of Patients with Exaggerated Blood Pressure Response During Treadmill Stress Test and Its Correlation with Risk Factors for Coronary Artery Disease

This study determined the prevalence and clinical profile of patients with Exaggerated Blood Pressure Response (EBPR) during Treadmill Exercise Test (TET) and its correlation with traditional risk factors of Coronary Artery Disease (CAD). <i>Methodology</i>: This is a cross-sectional study performed in Out Patient Department of Philippine General Hospital of patients 19 years old and above. Clinical profile was obtained and TET parameters including blood pressure at rest, during exercise and recovery period were determined. <i>Results</i>: There were 226 patients included in the study. The mean age is 52 and 121 (53.5%) were females. There were 108 (47.8%) with hypertension, 55 (24.3%) were smoker, 73 (32.3%) with dyslipidemia, 1 (0.4) with hyperuricemia, 31 (13.7) with diabetes, 51 (22.6%) with family history of CAD and 2 (3.9%) with history of supraventricular tachycardia (SVT). The prevalence of EBPR is 20.21%. Those with EBPR are usually female 31 (81.6%) and likely hypertensive 22 (57.9%). Female sex and abnormal BMI were the significant predictors of EBPR with p-value of 0.001 and 0.042 respectively. <i>Conclusion</i>: The prevalence of ESBR is 20.21%. The EBPR is strongly correlated with female sex and abnormal BMI. Further screening of these patient and aggressive management by adapting new HTN guidelines might help to reduce cardiovascular risk.

Исследование индивидуальных особенностей дыхательной системы спортсменов-лыжников в зависимости от физического состояния

Objective: to identify skiers individual respiratory system characteristics depending on their physical condition. Materials and methods: the study involved 20 professional skiers (10 men and 10 women, aged 23.2±0.9) who performed a long-term aerobic test (treadmill and bicycle ergometer) and a short-term anaerobic physical test (Wingate test on a bicycle ergometer). The gender and age specifi c data was processed and analyzed with generally accepted statistical methods. Before and after exercise, each subject underwent the individual respiratory system frequency characteristics and lung vital and forced vital capacity measurement to evaluate the physical activity effect on the respiratory system volume and frequency characteristics. The mean values in the reference groups and their standard deviations were calculated. Results: an analysis of the respiratory system frequency characteristics after physical exercise revealed a signifi cant change in resonance in men only in the exhalation phase after the “to failure” bicycle ergometric test, and in women only in the inhalation phase after treadmill test, all other frequency characteristics changes were insignifi cant. The maximum change in lung vital and forced vital capacity was found in men after treadmill stress test. The minimum change in lung vital and forced vital capacity was found in the male athletes after the “to failure” bicycle ergometer test. A signifi cant change in the resonant frequencies was found in the group of men only at the exhalation phase after “to failure” bicycle ergometer test., in women – only at the inhalation phase after the treadmill test. Conclusions: thus, the study revealed that both prolonged aerobic exercise and short anaerobic exercise do not result in signifi cant changes in the athletes’ respiratory system frequency characteristics suggesting the great potential of respiratory system bio-acoustic stimulation in sports medicine, since it can be performed at any period of the competitive training process at the time convenient for an athlete.

Renal Functional Reserve Is Related to the Nondipping Phenotype and to the Exercise Heart Rate Response in Patients with Essential Hypertension and Preserved Renal Function

Background: Renal functional reserve (RFR), defined as the difference between stress and resting glomerular filtration rate (GFR), may constitute a diagnostic tool to identify patients at higher risk of developing acute kidney injury or chronic kidney disease. Blunted RFR has been demonstrated in early stages of hypertension and has been attributed to impaired vascular reactivity due to an overactive sympathetic nervous system (SNS). Objective: The purpose of this study was to investigate whether RFR correlates with other phenotypes expressing overactivity of the SNS in patients with essential hypertension and preserved renal function. Methods: Thirty-six patients with untreated essential hypertension and a GFR >60 mL/min/1.73 m² were enrolled. The following parameters were measured: RFR, 24-h ambulatory blood pressure (BP) profile, a treadmill stress test, and an echocardiographic examination. Urine and venous samples were obtained at specific time points for the determination of clinical parameters, and both resting and stress GFR were calculated by using endogenous creatinine clearance for the measurement of RFR after an acute oral protein load (1 g/kg). Results: Twenty-one patients had a RFR <30 mL/min/1.73 m² and 15 had a RFR above this cutoff. A nondipping pattern of 24-h BP was significantly more frequent in patients with low RFR (57.1 vs. 25.0%, p < 0.05 for systolic BP and 52.3 vs. 10.0%, p < 0.02 for diastolic BP). Moreover, patients with lower RFR values showed a blunted heart rate (HR) response to exercise during treadmill test (r = 0.439, p < 0.05). None of the echocardiographic parameters differed between the two groups of patients. Conclusions: In hypertensive patients with preserved GFR, reduced RFR is related to nondipping BP phenotype as well as to attenuated exercise HR response. Overactivity of the SNS may be a common pathway. Since loss of RFR may represent a risk factor for acute or chronic kidney injury, hypertensive patients with blunted RFR might need a more careful renal follow-up.

P1398 Echocardiographic continuous monitoring of exercise stress test using probe fixation device

Abstract Background Stress echocardiography (SE) plays an important role among methods of noninvasive diagnosis of ischemic disease. Despite the advantages of physical exercise as the most physiologic stressor, it is difficult (bicycle ergometer) or impossible (treadmill) to obtain and maintain the acoustic window during the exercise. Recently, an innovative probe fixation device was introduced and a research plan was developed to assess the feasibility of external probe fixation during exercise echocardiography on a supine bicycle and upright treadmill exercise for the first time. Methods 37 subjects (36 men, mean age 39 ± 16 years, 21 healthy volunteers, 16 patients with suspected coronary artery disease) were included in this study. This preliminary testing stage included mostly men due to more problematic probe fixation in women. All subjects underwent a submaximal exercise stress test on a treadmill (17/37) or bicycle ergometer (11/37). Both sector and matrix probes were used. We assessed semi-quantitatively the quality of acquired apical views at each stage – the four-point grading system was used (0-no view, 1-suboptimal quality, 2-optimal quality, 3-very good quality), 2-3 sufficient for diagnosis. Results The mean time required for careful positioning of the probe and image optimization was 12 ± 3 min and shortened from 13,7 to 11,1 minutes (mean) in first vs second half of the cohort documenting learning curve. At baseline, 9 patients had at least one apical view of quality precluding reliable analysis. Those patients were excluded from further assessment. During stress, 17 patients maintained the optimal or very good quality of all apical views, whereas in 11 patients the quality significantly decreased during the stress test and required probe repositioning. The mean image quality score at baseline was 2,61 ± 0,48 and 2,25 ± 0,6 after exercise. Expectedly, good image quality was easier to obtain and maintain in the supine position (score 2,74 ± 0,44) points as compared with upright position (score 2,25 ± 0,57). Conclusion This preliminary, unique experience with external probe fixation device indicates that continuous acquisition and monitoring of echocardiographic images is feasible during physical exercise, and for the first time ever - also on the treadmill. This feasibility data stem from almost exclusively male patients and the estimated rate of sufficient image quality throughout the entire test is currently around 60%. We are hoping, that gaining more experience with the product could increase the success rate on exercise tests. Abstract P1398 Figure. Treadmill and ergometer stress test

VO2 Estimation Equation Accuracy to Young Adults

B&#x0D; Objective: analyze the agreement of the V̇O2max values estimated by American College of Sports Medicine‎ and Foster equations with direct measure gas analyze in young Brazilian males. The maximal oxygen uptake, as a health indicator and mortality predictor, can be assessed in different ways. The gold standard comprises the direct measurement of exhaled gases, which entails high cost. A more conveniently form can be estimation equations. Materials and methods: this study assessed VO2max of 41 young Brazilian males (21.4 ±2.2 years) by cardiopulmonary exercise test in a treadmill ergometer with a ramp protocol. Bland and Altman analysis was performed to verify the agreement between V̇O2max measured and estimated values by ACSM and Foster equations. Results: the measured VO2max was 52.3 ± 4.9 ml.kg-1.min-1. The difference between the measured V̇O2max and the estimated V̇O2max by the ACSM equation (9.40±3.67) was approximately 7.5 times greater than the difference between the measured V̇O2max and estimated V̇O2max by Foster's equation (1.25±3.46). Bland Altman graphics shows that only ACSM equation had mean differences that were significantly different from the measured value. Conclusions: the ACSM equation showed not appropriate for during treadmill stress testing young adults in a ramp protocol and Foster equation seems to be a more accurate estimator of V̇O2max for this population, besides showed a bias along the aerobic capacity, trending to overestimates and underestimates V̇O2max of least and most fit people, respectively.

Effects of clipping endoscopic thoracal sympathectomy at Th4 on cardiopulmonary functions, quality of life and psychosocial functions

In this study, we evaluated the cardiopulmonary and psychosocial effects of endoscopic thoracal sympathectomy (ETS) by clipping procedure at the level of Th4 and effects of ETS on quality of life of patients with hyperhidrosis. We performed a prospective study in 52 patients complaining of local sweating who applied to our clinic. Cardiac maximal treadmill stress test (CMTST), pulmonary function tests, Beck anxiety-depression inventory, Liebowitz social anxiety scale and SF-36 quality of life questionnaires were administered at preoperative period and postoperative 6th month. In the pulmonary function test, we found a minimal decrease in FEV1, and FEV1/FVC. There were no significant change in 'resting pulse rate', 'resting systolic and diastolic blood pressures' during CMTST between before and after operation. There was a significant difference in peak heart rate before CMTST, post-exercise diastolic blood pressure, and age-predictive maximal heart rate between before and after clipping procedure. In the SF-36 questionnaire, all parameters were improved. In the Beck depression-anxiety inventory and the Liebowitz social anxiety scale significant improvement was achieved in all parameters. ETS by clipping procedure at the Th4 level is advised to be a safe and effective method for management of hyperhidrosis patients.

A Curious Hand Rash Following Application of Vascular Compression Band to the Radial Artery

A 60-year-old man with history of hypertension, hyperlipidemia, and diabetes mellitus presented for a coronary angiogram after an abnormal electrocardiographic treadmill stress test for exertional chest pain. He underwent successful drug-eluting stent placement to a 75% mid–left anterior

TOPIRAMATE-INDUCED DYSPNEA: A RARE ADVERSE EFFECT

SESSION TITLE: Tuesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Migraine headaches are a common condition affecting about 12% of the general population, more common in women (17%) than men (6%) [1]. Migraine patients can benefit from a number of preventive drugs such as propranolol, valproate, and topiramate. Data suggests that topiramate is as effective as propranolol for migraine prevention and may be more beneficial than valproate. Among the many adverse effects of topiramate, dyspnea is one of it’s very rare side effects. We hereby report one such uncommon case of topiramate induced dyspnea CASE PRESENTATION: A 26-year-old female with a past medical history of migraines, on topiramate for nearly 1 year, presented to our emergency room with worsening dyspnea on exertion for 1 week. She was found to have an elevated D-dimer level (600ng/dl). Vital signs at the time of presentation were stable. There was no evidence of hypoxemia. She was admitted for further evaluation and underwent an extensive cardiopulmonary work up including a ventilation perfusion scan, computed tomography angiogram of the chest, lower extremity Doppler's, electrocardiogram, echocardiogram, chest x-ray, brain natriuretic peptide level, and thyroid function testing which were all within normal limits and failed to show any cause of her symptoms (Table 2). During her hospital course her shortness of breath (SOB) was easily reproducible with minimal ambulation without desaturation. She was discharged from the hospital and advised to follow with cardiology and pulmonary physicians. Her outpatient work up included pulmonary function testing and treadmill stress testing, which were again unrevealing. After further review of her case, her topiramate was discontinued as this was thought to be the possible cause of her dyspnea. Her SOB returned to normal within 3 days of discontinuation, establishing the diagnosis of topiramate induced dyspnea. DISCUSSION: Topiramate is an approved neuromodulator for migraine prophylaxis since 1996. It has 4 known mechanisms of action which include being a sodium channel blocker, potentiating gamma amino butyric acid, a glutamate antagonist, and inhibiting isoenzymes of carbonic anhydrase [2]. The first 3 mechanisms are responsible for its neurologic effect while the fourth induces a type 2 renal tubular acidosis leading to metabolic acidosis. While metabolic acidosis is a common side effect (35%) of topiramate, it rarely produces dyspnea (1-3%). There are only a few reported cases of topiramate induced dyspnea, first in 2007 [3]. All of the reported cases had no definitive cause for SOB identified after extensive work up, however all of those patients had improvement in their respiratory status once topiramate was discontinued within 72 hours as in our case CONCLUSIONS: Dyspnea is a rare adverse effect of topiramate which should be considered while evaluating a patient with dyspnea of unexplained origin after full cardiac and pulmonary workup are complete Reference #1: Lipton RB, Stewart WF, Diamond S, et al. Prevalence and burden of migraine in the United States: data from the American Migraine Study II. Headache 2001; 41:646 Reference #2: Montenegro M.A., Guerreiro M.M., Scotoni A.E., and Guerreiro C.A.: Predisposition to metabolic acidosis induced by topiramate. Arq Neuro-Psiquiatr 2000; 58: pp. 282-284 Reference #3: Delpirou-Nouh C, Gelisse P, Chanez P, Carlander B.: Migraine and topiramate induced dyspnea. Headache. 2007 Nov-Dec;47(10):1453-5. Epub 2007 Sep 12. DISCLOSURES: No relevant relationships by John Mikhail, source=Web Response No relevant relationships by Mohammed Shariff, source=Web Response

4097Validation of seven different exercise treadmill stress testing protocols in a large 25-year stress testing registry

Abstract Background While the Bruce protocol has been extensively validated, other modified exercise protocols with less workload burden are commonly used, though their prognostic value is not well established. Purpose We sought to assess whether exercise capacity (or workload achieved in metabolic equivalents of task [METs]) remains predictive of mortality across various exercise stress testing protocols. Methods In a 25-year stress testing registry spanning from 1991 to 2015, we identified 120,705 patients who underwent 7 different standardized symptom-limited exercise stress testing protocols: Bruce, Modified Bruce, Cornell 0%, Cornell 5%, Cornell 10%, Naughton, and modified Naughton. The choice of the protocol was dependent on the supervising exercise physiologist according to purpose of the test and the individual patient. The primary outcome was all-cause mortality. Results Mean age was 53.3±12.5 years and 59% were male. There were 74953 Bruce, 8368 modified Bruce, 2648 Cornell 0%, 9972 Cornell 5%, 20425 Cornell 10% 1226 Naughton, and 3113 modified Naughton individual protocols. A total of 8426 death occurred over 8.7 years of mean follow-up duration. Figure 1 shows that there was an inverse relationship between peak METs achieved and mortality across all 7 protocols. On multivariable analysis, increasing METs remained protective against death [adjusted HR of 0.46; 95% CI (0.44 - 0.48); p&lt;0.001] even after adjusting for the protocol chosen, age, gender, hypertension, diabetes, coronary disease, end-stage renal disease, smoking, and statin use. METS vs. mortality by protocol Conclusion Across 7 different exercise protocols with various workloads, the predicted exercise capacity remained predictive of mortality irrespective of the protocol chosen, patients' demographics and comorbidities. Different testing choices likely represent different estimated functional capacity.

LEFT ATRIAL STRAIN BY SPECKLE TRACKING ECHOCARDIOGRAPHY IS NOT PREDICTED FUNCTIONAL CAPACITY IN HYPERTENSIVE POPULATION WITH PRESERVED SYSTOLIC FUNCTION AND NORMAL RESTING LEFT ATRIAL PRESSURE

Abstract&#x0D; Background: Hypertension is associated with diastolic dysfunction and impaired exercise capacity. LA has a substantial role to provides an optimal left ventricle diastolic filling. In this study, we aimed to assess the left atrial strain through STE as a predictor of functional capacity in the hypertensive population.&#x0D; Methods: A total of 43 hypertensive women (mean age 50 ± 5.2 y.o; BMI 28.5± 4.1 Kg/m2) consecutively enrolled in this study. Patients with LVEF &lt;50% or significant valvular pathology excluded. Two-dimensional STE performed to asses LA strain parameters, including PALS , PACS, and conduit strain. Functional capacity assessed by treadmill stress test using Bruce protocol.&#x0D; Result: Mean PALS, PACS, and conduit strain in this study was lower than reference normal value 25.8%&lt; 39%; 12.4% &lt;17%; 13.5% &lt;23%, respectively). All of the subjects had a preserved systolic function (mean LVEF 72.5 ± 7.6%) and normal resting LA pressure (mean PCWP 11.96 ± 2.09). Left atrial strain parameters value in the low-fair functional capacity group was not significantly different to average-good functional capacity group (p&gt;0.05). Left atrial strain parameters value was not significantly correlated to exercise duration and achieved METS (P&gt;0.05). &#x0D; Conclusion: LA strain value in this study was below the standard reference limit. LA strain cannot predict functional capacity in the hypertensive population with preserved ejection fraction and normal resting LA pressure.

Diagnostic Value Of Qtc Dispersion And And Qt Dispersion Ratio Changes On Stress Test In Detecting Significance Of Coroner Lesion In Stable Angina Pectoris Patients

Background : Treadmill exercise test remains an important method and often used in the initial evaluation of patients with chest pain and can be a filter for more expensive invasive diagnostic. Increased QT dispersion (QTD) occurs because of the heterogeneity of ventricular repolarization because transient ischaemia during a treadmill stress test can be a marker of coronary artery disease (CAD) and can improve the accuracy of exercise tests to diagnose CAD, but this parameter is still controversial.&#x0D; &#x0D; Method : This is an analytic observational approach with a cross sectional study. Data was taken retrospectively at the Heart Center Installation at RSUP Dr. M. Djamil Padang, from March to April 2019, stable angina pectoris patient with a positive treadmill stress test who underwent coronary angiography as the subject. Bivariate analysis was performed on changes in QTcD (∆QTcD) and QTdR (∆QTdR) variables on the significance of coronary lesions by the chi-square method, after which a diagnostic test was based on receiver operating curve (ROC) analysis.&#x0D; &#x0D; Study Result : There were 122 subjects and found that older age, male and smoking were more common in groups with significant coronary lesions. Cut off point for ∆QTcD is ≥13 ms with a sensitivity of 87,1% and specificity 85,2% and AUC 95,1%, while ∆QTdR ≥5.5% with sensitivity 85,7% and specificity 81,9% and AUC 90,5% are related to significancy of coronary lesion. Obtained subjects with significant lesions generally had a value of ∆QTcD ≥ 13 ms (p &lt;0.001) and ∆QTdR ≥ 5.5% (p &lt;0.001).&#x0D; &#x0D; Conclusion : The use of ∆QTdR dan ∆QTdR parameters as ECG variables, which are easily obtained in evaluating stress tests, can improve the diagnostic accuracy of exercise tests. In addition, evaluation of ∆QTdR dan ∆QTdR can provide information about the incidence of CAD.&#x0D; Keywords : ∆QTcD, ∆QTdR, Treadmill Exercise Test, Coronary Lession Significancy&#x0D;

Impaired heart rate recovery as a predictor for poor health-related quality in patients with transient ischemic attack.

We aimed to investigate heart rate recovery (HRR) in patients with transient ischemic attack (TIA) and the relationship between HRR and health-related quality of life (HRQOL).All available patients were enrolled during the enrollment period. A total of 120 patients with TIA and 120 healthy controls were included in this study. A treadmill stress test was performed to calculate the HRR. The HRR were calculated as follows: HRR 1, 2, 3, and 5 minutes = heart rate at peak during exercise − heart rate at 1, 2, 3, and 5 minutes at rest. All patients enrolled were asked to fill in the Short Form 36 Health Survey to calculate HRQOL.We found that the maximum heart rate of TIA patients was significantly higher than that of healthy controls (166 ± 11 vs. 162 ± 14 beats/min, P = .015). Similarly, maximum systolic blood pressure (SBP) and diastolic blood pressure (DBP) were higher in TIA group compared with healthy control group (SBP: 172 ± 15 vs. 165 ± 14 mm Hg, P < .001; DBP: 102 ± 12 vs. 93 ± 16 mm Hg, P < .001). The HRR were significantly lower in TIA group compared with control group (TIA vs. controls, HRR1: 17 ± 7 vs. 30 ± 8 beats/min, HRR2: 32 ± 11 vs. 49 ± 9 beats/min, HRR3: 43 ± 13 vs. 63 ± 12 beats/min, HRR5: 54 ± 16 vs. 73 ± 15 beats/min, all P < .001). Multivariate analysis showed that older age (P = .03) and high BMI (P = .04) were risk factors associated with abnormal HRR in patients with TIA. With regard to HRQOL, we found that role limitations due to physical problems, general health, vitality, and role limitations due to emotional problems were significantly lower in patients with abnormal HRR compared with patients with normal HRR. Multivariate analysis showed that older age (P = .04) and abnormal HRR (P = .03) were predictors for poor HRQOL in TIA patients.HRR was impaired in patients with TIA. In addition, TIA patients with abnormal HRR suffered from a significantly poorer HRQOL. Hence, given the prognostic value of HRR, patients with TIA should be monitored to prevent cardiovascular events and to improve HRQOL.

On the interpretability of machine learning-based model for predicting hypertension

BackgroundAlthough complex machine learning models are commonly outperforming the traditional simple interpretable models, clinicians find it hard to understand and trust these complex models due to the lack of intuition and explanation of their predictions. The aim of this study to demonstrate the utility of various model-agnostic explanation techniques of machine learning models with a case study for analyzing the outcomes of the machine learning random forest model for predicting the individuals at risk of developing hypertension based on cardiorespiratory fitness data.MethodsThe dataset used in this study contains information of 23,095 patients who underwent clinician-referred exercise treadmill stress testing at Henry Ford Health Systems between 1991 and 2009 and had a complete 10-year follow-up. Five global interpretability techniques (Feature Importance, Partial Dependence Plot, Individual Conditional Expectation, Feature Interaction, Global Surrogate Models) and two local interpretability techniques (Local Surrogate Models, Shapley Value) have been applied to present the role of the interpretability techniques on assisting the clinical staff to get better understanding and more trust of the outcomes of the machine learning-based predictions.ResultsSeveral experiments have been conducted and reported. The results show that different interpretability techniques can shed light on different insights on the model behavior where global interpretations can enable clinicians to understand the entire conditional distribution modeled by the trained response function. In contrast, local interpretations promote the understanding of small parts of the conditional distribution for specific instances.ConclusionsVarious interpretability techniques can vary in their explanations for the behavior of the machine learning model. The global interpretability techniques have the advantage that it can generalize over the entire population while local interpretability techniques focus on giving explanations at the level of instances. Both methods can be equally valid depending on the application need. Both methods are effective methods for assisting clinicians on the medical decision process, however, the clinicians will always remain to hold the final say on accepting or rejecting the outcome of the machine learning models and their explanations based on their domain expertise.

The Interplay of the Global Atherosclerotic Cardiovascular Disease Risk Scoring and Cardiorespiratory Fitness for the Prediction of All-Cause Mortality and Myocardial Infarction: The Henry Ford ExercIse Testing Project (The FIT Project)

Cardiorespiratory fitness (CRF) is inversely associated with atherosclerotic cardiovascular disease (ASCVD) risk. It is unclear whether the prognostic value of CRF differs by baseline estimated ASCVD risk. We studied a retrospective cohort of patients without known heart failure or myocardial infarction (MI) who underwent treadmill stress testing. CRF was measured by metabolic equivalents of task (METs) and ASCVD risk was calculated using the Pooled Cohorts Equations. Multivariable-adjusted Cox regressions analyses examined the association between METs and incident all-cause mortality and MI outcomes stratified by baseline ASCVD risk. The C-index evaluated risk discrimination while net reclassification improvement evaluated reclassification with CRF added to the ASCVD risk score. Our study population consisted of 57,999 patients of mean age 53 (13) years, 49% women, 64% white, 29% black. Over a median follow-up 11 years (interquartile range 8 to 14 years) there were 6,670 (11%) deaths, while there were 1,757 (3.0%) MIs over a median follow-up of 6 years (interquartile range 3 to 8 years). Among patients with ASCVD risk ≥20%, those with METs ≥12 had a 77% lower risk of all-cause mortality (Hazard ratio 0.23 95% confidence interval = 0.20, 0.27) and 67% lower risk of MI (Hazard ratio 0.33 95% confidence interval = 0.24, 0.46) compared to METs <6. Similar results were obtained for those with ASCVD risk <5%. Addition of METs to ASCVD risk score improved the C-statistic from 0.778 to 0.798 for all-cause mortality and 0.726 to 0.733 for MI (both p <0.001). Addition of METs to ASCVD risk score significantly reclassified risk of all-cause mortality (p <0.001) but not MI (p = 0.052). In conclusion, CRF is inversely associated with risk of all-cause mortality and MI at all levels of ASCVD risk, and provides incremental risk discrimination and reclassification beyond the ASCVD risk score.

Coronary artery calcium testing: A call for universal coverage.

Heart attacks kill more Americans than all cancers combined. Fatal heart attack victims have no symptoms until minutes before they die, hence early detection of high-risk asymptomatic individuals is needed. Even though heart attacks kill and cost more than cancers, as a nation we spend over 20 times more on screening for asymptomatic cancer than for asymptomatic atherosclerotic cardiovascular disease (ASCVD), the underlying cause of heart attacks. Currently, payers only cover screening for risk factors of ASCVD such as blood pressure and blood cholesterol. This approach tends to miss high-risk and over-treat low-risk individuals. Although treadmill stress testing with ECG is not indicated for ASCVD detection in asymptomatic individuals, it is done often, and frequently leads to misleading conclusions or unnecessary downstream diagnostic procedures. For example, former President Clinton had passed his treadmill stress tests for several years during his presidential annual checkup but had a heart attack shortly after his presidency. This common practice is a waste of our limited resources. Instead, a more accurate risk assessment using coronary artery calcium (CAC) testing is available; and has just been adopted by ACC/AHA guidelines, however payers do not cover it. CAC is measured non-invasively with a 5-minute CT-scan of the heart, and costs less than $200, whereas cancer screening with colonoscopy and mammography costs over $3000. There is an opportunity to save lives and dollars if CAC testing is covered for appropriately selected individuals. Texas has already passed HB1290 to mandate CAC coverage. Other states must step up and take actions.

Incremental Prognostic Value of Exercise Stress Testing in Primary Prevention

In primary prevention, addition of C-reactive protein and family history to standard risk factor assessment (Reynolds Risk Score or RRS) provides superior risk stratification for future cardiovascular (CV) events. We sought to assess whether addition of functional capacity to RRS provided incremental prognostic value. This was a prospective observational cohort study of 3,964 consecutive asymptomatic adults without documented CV disease (mean age 51 years, 78% men) evaluated between 2005 and 2013, who underwent clinical and treadmill stress testing at baseline. RRS was calculated; % age-gender predicted metabolic equivalents (AGP-METs) achieved and heart rate recovery (HRR) were recorded. End point was death and myocardial infarction. Findings were tested in derivation (n = 1,982) and validation samples (n = 1,982). Mean RRS and C-reactive protein were 3.7 ± 4 and 2 ± 4 mg/dl. Nine percent had family history of premature CV disease. %AGP-METs achieved, and HRR were 113 ± 20 and 24 ± 8 beats/min. Forty-six percent achieved <110% AGP-METs, whereas 41% had RRS ≥3. At 7.3 ± 3 years, there were 83 (2%) events (39 in derivation and 44 in validation samples). In derivation group, on multivariable survival analysis, higher RRS (Hazard ratio or HR 1.27 [1.07 to 1.39]), lower % AGP METs (HR 1.21 [1.09 to 1.34]) achieved and abnormal (<12 beats/min) HRR (HR 1.15 [1.02 to 1.23]) were associated with increased longer-term events (all p <0.01). Findings were similar in validation group. Cutoffs of RRS >3 and %AGP-METs <110 were associated with increased longer-term events on spline analysis in the derivation group. The continuous net reclassification improvement for longer-term events, when %AGP-METs was added to RRS was 0.79 (95% confidence interval 0.52 to 1.05; p <0.01). Findings were confirmed in validation group. In conclusion, in primary prevention, addition of exercise capacity to RRS (incorporating traditional risk factors, family history, and inflammation) provides incremental prognostic value.

Electrocardiogram-Derived Tidal Volume During Treadmill Stress Test.

Electrocardiogram (ECG) has been regarded as a source of respiratory information with the main focus in the estimation of the respiratory rate. Although little research concerning the estimation of tidal volume (TV) has been conducted, there are several ECG-derived features that have been related with TV in the literature, such as ECG-derived respiration, heart rate variability, and respiratory rate. In this paper, we exploited these features for estimating TV using a linear model. 25 young (33.4 ± 5.2 years) healthy male volunteers were recruited for performing a maximal (MaxT) and a submaximal (SubT) treadmill stress test, which were conducted on different days. Both tests were automatically segmented in stages attending to the heart rate. Afterwards, a subject-specific TV model was calibrated for each stage, employing features from MaxT, and the model was later used for estimating the TV in SubT. During exercise, the different proposed approaches led to relative fitting errors lower than 14% in most of the cases and 6% in some of them. Low achieved fitting errors suggest that TV can be estimated from ECG during a treadmill stress test. The results suggest that it is possible to estimate TV during exercise using only ECG-derived features.

Abstract 163: Economy of Handheld Ultrasound in an Outreach Clinic Setting

Introduction: The usefulness of Handheld Ultrasound (HHU) is increasingly recognized in a variety of settings. This study demonstrates the ability of HHU to dramatically reduce costs in the clinic setting. Objectives: An HHU was implemented in 2018 to perform bedside echocardiograms at the USF outreach clinic (BRIDGE) with the expectation of cost savings. Methods: The implementation of the HHU at the BRIDGE clinic began in early 2018. Prior to 2018, all BRIDGE patients requiring any cardiac tests were referred to the separate USF Cardiology clinic. Following the implementation of the HHU at the BRIDGE clinic, all necessary echocardiograms were performed initially with the HHU in-clinic with additional testing referred to USF Cardiology, if needed. Data on all BRIDGE clinic patients who received cardiac care in 2017 was compiled and compared to all clinic patients who received cardiac care in 2018, after the implementation of the HHU. Primary variables compared by patient were number of follow-up visits, and number and type of tests ordered (complete and stress echocardiograms, treadmill and nuclear stress tests, and ambulatory monitors). An analysis was then conducted to determine differences in visits and overall costs by BRIDGE clinic patients before and after HHU implementation. Cost data for tests was obtained from the USF financial department. Results: In 2017, 17 patients were seen in BRIDGE clinic that were subsequently referred to cardiology for further care/testing. In 2018, 20 cardiac patients were evaluated in BRIDGE clinic and 25% required further testing. Across 2017 patients, there was an average of 1.53 cardiology follow-up visits and 1.47 cardiac tests conducted per patient, while overall tests costs averaged $383.77 per patient. In comparison, across 2018 patients there was an average of 0.4 cardiology follow-up visits and 0.3 cardiac tests conducted per patient, while overall test costs averaged $284.40 across patients who received further testing. This represents an 25.9% decrease in cost after implementation of HHU. Conclusions: These results demonstrate that BRIDGE clinic patients after HHU implementation had both less cardiology follow-up visits and tests conducted, which led to lower overall costs. This was largely due to the significant reduction in the number of complete echocardiogram tests ordered as these were performed in-clinic with the lower-cost HHU.