COVID-19-Induced Changes in Photoplethysmography.

INTRODUCTION: Photoplethysmography (PPG) is the science behind many commonly used medical devices such as the pulse oximeter. PPG changes, herein as "PPG dropouts," have been described in existing in vitro studies following artificially induced clot activation. Because COVID-19 causes increased arterial, venous, and microvascular clot formation, our hypothesis is that PPG dropouts identified in vitro can also be found in vivo in patients with COVID-19. The aim of this study is to evaluate PPG recordings and D-dimer levels for patients hospitalized with COVID-19 and compare them with the PPG tracings from non-COVID controls. MATERIALS AND METHODS: PPG recordings were obtained for 197 ICU patients with COVID-19 and 300 non-COVID controls. PPG tracings were obtained using a TigerTech CovidPlus monitor, which received U.S. FDA emergency use authorization in March 2020 for monitoring the biometrics of patients with COVID-19 and featured unfiltered red and infrared spectrum PPG monitoring. D-dimer lab results were also recorded whenever available. RESULTS: The results demonstrated significant differences in the prevalence rate of PPG dropout among patients with COVID-19 vs. non-COVID controls. The median PPG dropout rate was 0.58 for COVID-19 patients (median 0.58, IQR 0.42-0.72, P < .05) as opposed to a median 0.0 for non-COVID patients (median 0.0, IQR 0.0-0.0, P < .05). Furthermore, at least one incidence of PPG dropout was detected in 100% of COVID-19 patients, as opposed to 2.3% of non-COVID controls (P < .05). PPG dropout also correlated closely with the normalized serum D-dimer levels taken on the same day. The change in the normalized D-dimer levels was plotted against the change in PPG dropout, and a line of best fit was created. Linear regression resulted in R2 = 0.743 (P < .05), indicating that changes in the PPG dropout rate correlate with hemorheological changes in COVID-19 patients. CONCLUSIONS: PPG dropout, like D-dimer, may not be specific for COVID-19. However, the inflammatory nature of the disease and the prevalence of prolonged ICU created a large sample size and allowed the authors to observe PPG changes in vivo in a statistically meaningful way. Further confirmatory studies are needed to confirm the potential application of PPG dropout as a measure of inflammation in other disease processes.

Heart Rate Variability as a Possible Predictive Marker for Acute Inflammatory Response in COVID-19 Patients.

INTRODUCTION: Increases in C-reactive protein (CRP) are used to track the inflammatory process of COVID-19 and are associated with disease state progression. Decreases in heart rate variability (HRV) correlate with worsening of disease states. This observational study tracks changes in HRV relative to changes in CRP in COVID-19 patients. MATERIALS AND METHODS: In accordance with an Institutional Review Board-approved study, 17 patients were followed using the wearable, noninvasive Tiger Tech Warfighter Monitor (WFM) that records HRV from a single limb electrocardiogram. Intermittent, daily short-segment data sets of 5 to 7 minutes over a minimum of 7 days were analyzed. Changes in HRV were compared to changes in CRP. RESULTS: Decreases in HRV of greater than 40% preceded a 50% increase in CRP during the ensuing 72 hours in 10 of the 12 patients who experienced a dramatic rise in CRP. The effectiveness of HRV as a leading indicator of a rise in CRP was evaluated; the sensitivity, specificity, positive predictive value, and negative predictive value for 40% decreases in HRV preceding 50% increases in CRP were 83.3%, 75%, 90.9%, and 60%, respectively. CONCLUSION: Substantial decreases in HRV preceded elevations in CRP in the ensuing 72 hours with a 90.9% positive predictive value. Early detection of increasing inflammation may prove vital in mitigating the deleterious effects of an abnormal inflammatory response, particularly in COVID-19 patients. This capability could have a major impact in triage and care of moderate to severe COVID-19 patients in major medical centers as well as field hospitals. This study demonstrates the potential value of short-segment, intermittent HRV analysis in COVID-19 patients.

Outcomes of minimally invasive double valve surgery.

BACKGROUND: Double valve surgery is associated with an increased peri-operative morbidity and mortality. A less invasive right thoracotomy approach may be a viable alternative to median sternotomy surgery in these higher-risk patients. METHODS: We retrospectively analyzed the baseline demographics, operative characteristics, and post-operative outcomes of patients who underwent minimally invasive double valve surgery between January 2009 and December 2011 at our institution. RESULTS: The cohort consisted of 117 patients, of which 68 (58.1%) were female. The mean age was 73±11 years, and the mean left ventricular ejection fraction was 52±11%. There were 43 (36.8%) patients with a history of congestive heart failure, 45 (38.5%) with chronic obstructive pulmonary disease, and 5 (4.3%) had a history of chronic kidney disease. The patients underwent primary (90.6%) or re-operative (9.4%) double valve surgery, which consisted of 50 (42.7%) aortic valve replacement and mitral valve repair, 31 (26.5%) mitral and tricuspid valve repair, 18 (15.4%) aortic and mitral valve replacement, 17 (14.5%) mitral valve replacement with tricuspid valve repair, and 1 (0.9%) aortic valve replacement with tricuspid valve repair. Post-operatively, there were 40 (34.2%) cases of prolonged ventilation, 9 (7.7%) acute kidney injury, 6 (5.1%) re-operations for bleeding, 1 (0.9%) cerebrovascular accident, and 15 (12.8%) cases of atrial fibrillation. The mean total hospital length of stay was 12±12 days, with an in-hospital mortality of 2 (1.7%). CONCLUSIONS: A minimally invasive right thoracotomy approach to primary or re-operative double valve surgery is feasible, may be utilized with acceptable peri-operative morbidity and mortality.

Percutaneous Coronary Intervention Followed by Minimally Invasive Mitral Valve Surgery in Ischemic Mitral Regurgitation.

OBJECTIVE: The optimal treatment strategy in patients with coronary artery disease and ischemic mitral regurgitation (IMR) remains controversial. A staged approach of percutaneous coronary intervention (PCI) followed by minimally invasive valve surgery, rather than combined median sternotomy coronary artery bypass and valve surgery, may be a viable alternative. METHODS: We retrospectively evaluated 31 consecutive patients with coronary artery disease and severe IMR who underwent a staged procedure at our institution between February 2009 and April 2014. RESULTS: The mean ± SD age, preoperative left ventricular ejection fraction, and mitral regurgitation grade were 72 ± 7 years, 35% ± 11%, and 3.6 ± 0.6, respectively. The mean ± SD Society of Thoracic Surgeons-predicted mortality score was 5.1% ± 4.2%. Percutaneous coronary intervention was performed for 1- and 2-vessel disease in 22 patients (71%) and 9 patients (29%), respectively, with 23 patients (74%) having drug-eluting stents placed. Minimally invasive valve surgery was performed within a median of 36 days after PCI, with 61% of the patients being on dual antiplatelet therapy. Postoperatively, there was 1 case of acute kidney injury, 1 case of reoperation for bleeding, and no cerebrovascular accidents. The 30-day mortality was 3%. The median total hospital length of stay was 8 days (interquartile range, 7-10). At a mean ± SD follow-up of 2.4 ± 1.6 years, 2 patients required PCI for target-vessel revascularization. Actuarial survival at 1 and 5 years was 84% and 80%, respectively. CONCLUSIONS: A staged approach in patients with coronary artery disease and IMR can be performed with a low perioperative morbidity and good midterm survival.