Browsing by Author "Kumar, Awaneesh"

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    Effects of anesthetic and sedative agents on sympathetic nerve activity
    (Elsevier, 2019) Liu, Xiao; Rabin, Perry Lee; Yuan, Yuan; Kumar, Awaneesh; Vasallo, Peter, III; Wong, Johnson; Mitscher, Gloria A.; Everett, Thomas H., IV; Chen, Peng-Sheng; Medicine, School of Medicine
    Background The effects of sedative and anesthetic agents on sympathetic nerve activity (SNA) are poorly understood. Objective The purpose of this study was to determine the effects of commonly used sedative and anesthetic agents on SNA in ambulatory dogs and humans. Methods We implanted radiotransmitters in 6 dogs to record stellate ganglion nerve activity (SGNA), subcutaneous nerve activity (ScNA), and blood pressure (BP). After recovery, we injected dexmedetomidine (3 μg/kg), morphine (0.1 mg/kg), hydromorphone (0.05 mg/kg), and midazolam (0.1 mg/kg) on different days. We also studied 12 human patients (10 male; age 68.0 ± 9.1 years old) undergoing cardioversion for atrial fibrillation with propofol (0.77 ± 0.18 mg/kg) or methohexital (0.65 mg/kg) anesthesia. Skin sympathetic nerve activity (SKNA) and electrocardiogram were recorded during the study. Results SGNA and ScNA were significantly suppressed immediately after administration of dexmedetomidine (P = .000 and P = .000, respectively), morphine (P = .011 and P = .014, respectively), and hydromorphone (P = .000 and P = .012, respectively), along with decreased BP and heart rate (HR) (P <.001 for each). Midazolam had no significant effect on SGNA and ScNA (P = .248 and P = .149, respectively) but increased HR (P = .015) and decreased BP (P = .004) in ambulatory dogs. In patients undergoing cardioversion, bolus propofol administration significantly suppressed SKNA (from 1.11 ± 0.25 μV to 0.77 ± 0.15 μV; P = .001), and the effects lasted for at least 10 minutes after the final cardioversion shock. Methohexital decreased chest SKNA from 1.59 ± 0.45 μV to 1.22 ± 0.58 μV (P = .000) and arm SKNA from 0.76 ± 0.43 μV to 0.55 ± 0.07 μV (P = .001). The effects lasted for at least 10 minutes after the cardioversion shock. Conclusion Propofol, methohexital, dexmedetomidine, morphine, and hydromorphone suppressed, but midazolam had no significant effects on, SNA.
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    Fragmented Left Sided QRS in Absence of Bundle Branch Block: Sign of Left Ventricular Aneurysm
    (Wiley, 2006-03-28) Reddy, Chatla V. R.; Cheriparambill, Kuruvilla; Saul, Barry; Makan, Majesh; Kassotis, John; Kumar, Awaneesh; Das, Mithilesh Kumar; Medicine, School of Medicine
    Background: A left ventricular aneurysm (LVA) occurs between 3.5% and 9.4% of all cases of acute myocardial infarction. A fragmented left sided QRS (RSR` pattern or its variant RSr`, rSR`, or rSr`) without evidence of bundle branch block (QRS duration ≤120 ms) on the ECG may be associated with a significant myocardial scar, which is the characteristic of a LVA. We, therefore, postulate that fragmented QRS (RSR` pattern or its variant) in the left sided leads (I, aVL, V3 to V6) may be a useful sign of LVA. Methods: ECGs of 110 consecutive patients with LVA documented by left ventricular angiography (30° right anterior oblique view) was compared with 220 patients without LVA (110 patients with and 110 patients without coronary artery disease (CAD)), who were evaluated for CAD by symptoms and signs. Results: The sensitivity of the fragmented QRS for identification of LVA was 50% (55 of 110 patients) and specificity was 94.6% (209 of 220). Within the study population, the positive predictive value of the fragmented QRS for LVA was 83.3% (55 of 66) and the negative predictive value was 79.2% (209 of 264). Based on the range of prevalence of LVA in postmyocardial infarction population (3.5–9.4%) and on observed sensitivity and specificity, the positive predictive value of fragmented QRS for LVA after infarction can be estimated at 29–53% and the negative predictive value can be estimated at 95–98%. Conclusion: The sensitivity of fragmented QRS in left precordial leads for LVA was only 50%, whereas the specificity was 94.5%. It has a relatively low to moderate positive predictive value and high negative predictive value.
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    Skin Sympathetic Nerve Activity as a Biomarker for Neurological Recovery during Therapeutic Hypothermia for Cardiac Arrest
    (Elsevier, 2021) Kutkut, Issa; Uceda, Domingo; Kumar, Awaneesh; Wong, Johnson; Li, Xiaochun; Wright, Keith C.; Straka, Susan; Adams, David; Deckard, Michelle; Kovacs, Richard; Chen, Peng-Sheng; Everett, Thomas H., IV.; Medicine, School of Medicine
    Background: Targeted temperature management (TTM) improves neurologic outcome after cardiac arrest. However, better neurologic prognostication is needed. Objective: The purpose of this study was to test the hypothesis that noninvasive recording of skin sympathetic nerve activity (SKNA) and its association with heart rate (HR) during TTM may serve as a biomarker of neurologic status. Methods: SKNA recordings were analyzed from 29 patients undergoing TTM. Patients were grouped based on Clinical Performance Category (CPC) score into group 1 (CPC 1-2) representing a good neurologic outcome and group 2 (CPC 3-5) representing a poor neurologic outcome. Results: Of the 29 study participants, 18 (62%) were deemed to have poor neurologic outcome. At all timepoints, low average skin sympathetic nerve activity (aSKNA) was associated with poor neurologic outcome (odds ratio 22.69; P = .002) and remained significant (P = .03) even when adjusting for presenting clinical factors. The changes in aSKNA and HR during warming in group 1 were significantly correlated (ρ = 0.49; P <.001), even when adjusting for corresponding temperature and mean arterial pressure measurements (P = .017), whereas this correlation was not observed in group 2. Corresponding to high aSKNA, there was increased nerve burst activity during warming in group 1 compared to group 2 (0.739 ± 0.451 vs 0.176 ± 0.231; P = .013). Conclusion: Neurologic recovery was retrospectively associated with SKNA. Patients undergoing TTM who did not achieve neurologic recovery were associated with low SKNA and lacked a significant correlation between SKNA and HR. These preliminary results indicate that SKNA may potentially be a useful biomarker to predict neurologic status in patients undergoing TTM.
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    Skin Sympathetic Nerve Activity as a Biomarker for Syncopal Episodes during a Tilt Table Test
    (Elsevier, 2020-05) Kumar, Awaneesh; Wright, Keith; Uceda, Domingo E.; Vasallo, Peter A., III.; Rabin, Perry L.; Adams, David; Wong, Johnson; Das, Mithilesh; Lin, Shien-Fong; Chen, Peng-Sheng; Everett, Thomas H., IV.; Medicine, School of Medicine
    Background: Autonomic imbalance is the proposed mechanism of syncope during a tilt table test (TTT). We have recently demonstrated that skin sympathetic nerve activity (SKNA) can be noninvasively recorded using electrocardiographic electrodes. Objective: The purpose of this study was to test the hypothesis that increased SKNA activation precedes tilt-induced syncope. Methods: We studied 50 patients with a history of neurocardiogenic syncope undergoing a TTT. The recorded signals were band-pass filtered at 500-1000 Hz to analyze nerve activity. Results: The average SKNA (aSKNA) value at baseline was 1.38 ± 0.38 μV in patients without syncope and 1.42 ± 0.52 μV in patients with syncope (P = .77). On upright tilt, aSKNA was 1.34 ± 0.40 μV in patients who did not have syncope and 1.39 ± 0.43 μV in patients who had syncope (P = .65). In all 14 patients with syncope, there was a surge of SKNA before an initial increase in heart rate followed by bradycardia, hypotension, and syncope. The peak aSKNA immediately (<1 minute) before syncope was significantly higher than baseline aSKNA (2.63 ± 1.22 vs 1.39 ± 0.43 μV; P = .0005). After syncope, patients were immediately placed in the supine position and aSKNA dropped significantly to 1.26 ± 0.43 μV; (P = .0004). The heart rate variability during the TTT shows a significant increase in parasympathetic tone during syncope (low-frequency/high-frequency ratio: 7.15 vs 2.21; P = .04). Conclusion: Patients with syncope do not have elevated sympathetic tone at baseline or during the TTT except immediately before syncope when there is a transient surge of SKNA followed by sympathetic withdrawal along with parasympathetic surge.
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    Skin Sympathetic Nerve Activity as a Biomarker of Fitness
    (Elsevier, 2021) Liu, Xiao; Kumar, Awaneesh; O’Neil, Joseph; Wong, Johnson; Saadoon, Osama; Kadire, Siri; Mitscher, Gloria A.; Li, Xiaochun; Chen, Peng-Sheng; Emery, Michael S.; Everett, Thomas H., IV; Biostatistics, School of Public Health
    Background: Exercise stress testing is frequently used to expose cardiac arrhythmias. Aerobic exercise conditioning has been used as a nonpharmacologic antiarrhythmic intervention. Objective: The purpose of this study was to test the hypothesis that noninvasively recorded skin sympathetic nerve activity (SKNA) is increased during exercise and that SKNA response varies according to fitness levels. Methods: Oxygen consumption (VO2) and SKNA were recorded in 39 patients undergoing an incremental exercise test. Patients were grouped by 5 levels of fitness based on age, sex, and VO2max. Results: With exercise, all patients had a significant increase in average SKNA (aSKNA) (1.58 ± 1.12 μV to 4.50 ± 3.06 μV, P = .000) and heart rate (HR) (87.40 ± 20.42 bpm to 154.13 ± 16.82 bpm, P = .000). A mixed linear model of aSKNA was used with fixed effects of fitness, exercise time, and recovery time, and random effects of subject level intercept and slopes for exercise time and recovery times. The poor fitness group had significantly higher aSKNA than the other groups (P = .0273). For all subjects studied, aSKNA increased by 5% per minute with progression of exercise and decreased by 15% per minute with progression of recovery. The fitness variable encodes information on both comorbidities and body mass index (BMI). Once fitness level is known, comorbidities and BMI are not significantly associated with aSKNA. In all groups, aSKNA positively correlated with HR (R2 = 0.47 ± 0.23) and VO2 (R2 = 0.68 ± 0.25). Conclusion: Fitness level determines the magnitude and time course of SKNA increase during exercise. SKNA may be a useful fitness biomarker in exercise stress testing.