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Dive into the research topics where Christopher K. Johnson is active.

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Featured researches published by Christopher K. Johnson.


Pacing and Clinical Electrophysiology | 2014

Comparative Safety of Periablation Anticoagulation Strategies for Atrial Fibrillation: Data from a Large Multicenter Study

Aysha Arshad; Christopher K. Johnson; Suneet Mittal; Eric Buch; Ismail Hamam; Thanh Tran; Richard E. Shaw; Dan Musat; Mark Preminger; Tina Sichrovsky; Bengt Herweg; Kalyanam Shivkumar; John Hummel; Jonathan S. Steinberg

There are a variety of periprocedural anticoagulation strategies for atrial fibrillation (AF) ablation, including the use of dabigatran. It is unclear which strategy is superior.


European Journal of Cardio-Thoracic Surgery | 2016

The effects of using a radial artery in patients already receiving bilateral internal mammary arteries during coronary bypass grafting: 30-day outcomes and 14-year survival in a propensity-matched cohort

Juan B. Grau; Cyrus E. Kuschner; Christopher K. Johnson; Giovanni Ferrari; Alex Zapolanski; Mariano E. Brizzio; Richard E. Shaw

OBJECTIVES Recent studies have demonstrated the superiority of bilateral internal mammary arteries (BIMAs) as conduit material for coronary artery bypass grafting (CABG) surgery. However, there is limited research on the effects of other graft conduits used in patients who require additional bypasses. The goal of this study was to evaluate the impact of the radial artery (RA) when used in conjunction with the BIMAs. METHODS From the beginning of 2000 to the end of 2013, 4370 patients underwent CABG for three or more vessels at our institution. There were 568 and 183 patients who received BIMA + saphenous vein graft (SVG) and BIMA + radial ± SVG, respectively. Propensity matching was used to create a balanced cohort from these patients, which resulted in two groups of 183 patients. Thirty-day outcomes and long-term survival were compared between the two groups. Long-term follow-up was generated using the Social Security Death Index. RESULTS There were no significant differences in preoperative characteristics. For 30-day outcomes, the BIMA + radial ± SVG group had more postoperative atrial fibrillation (24.6 vs 12.0%; P = 0.001) and a longer median postoperative length of stay (6 vs 5 days; interquartile range = 2; P = 0.016) than BIMA + SVG patients. There was no significant difference in long-term survival between the two groups over the 14-year period. However, before year 10, the BIMA + SVG group had a trend towards higher survival, whereas on follow-up after 10 years, there was a trend that favoured the BIMA + radial ± SVG patients. Cox regression analysis using a time-dependent covariate demonstrated that when the groups were split at 10 years, there was a statistically significant improvement in survival of the BIMA + radial ± SVG group [adjusted hazard ratio 0.254 95% confidence interval (CI) 0.062-0.977; P = 0.048] over BIMA + SVG patients between 10 and 14 years. CONCLUSIONS Overall, there were no statistically significant differences in survival between the BIMA + SVG and BIMA + radial ± SVG groups over the 14 years. However, further analysis demonstrated that while the BIMA + radial ± SVG group had a trend towards decreased survival before 10 years, use of the RA in conjunction with BIMAs was associated with significantly increased survival in the later years. A larger cohort of patients with longer follow-up is needed to assess the outcomes of CABG using BIMA + radial ± SVG.


Transfusion | 2014

Blood transfusion in cardiac surgery does increase the risk of 5‐year mortality: results from a contemporary series of 1714 propensity‐matched patients

Richard E. Shaw; Christopher K. Johnson; Giovanni Ferrari; Mariano E. Brizzio; Kathleen Sayles; Nancy Rioux; Alex Zapolanski; Juan B. Grau

Studies have found that cardiac surgery patients receiving blood transfusions are at risk for increased mortality during the first year after surgery, but risk appears to decrease after the first year. This study compared 5‐year mortality in a propensity‐matched cohort of cardiac surgery patients.


Transfusion | 2014

Transfusion-related acute lung injury and potential risk factors among the inpatient US elderly as recorded in Medicare claims data, during 2007 through 2011.

Mikhail Menis; Steven A. Anderson; Richard A. Forshee; Stephen McKean; Christopher K. Johnson; Rob Warnock; Rahul Gondalia; Paul D. Mintz; Leslie Holness; Christopher M. Worrall; Jeffrey A. Kelman; Hector S. Izurieta

Transfusion‐related acute lung injury (TRALI) is a serious complication leading to pulmonary edema and respiratory failure. This studys objective was to assess TRALI occurrence and potential risk factors among inpatient US elderly Medicare beneficiaries, ages 65 and older, during 2007 through 2011.


Interactive Cardiovascular and Thoracic Surgery | 2013

Balancing the benefits and risks of blood transfusions in patients undergoing cardiac surgery: a propensity-matched analysis

Richard E. Shaw; Christopher K. Johnson; Giovanni Ferrari; Alex Zapolanski; Mariano E. Brizzio; Nancy Rioux; Srinivasa Edara; Jason S. Sperling; Juan B. Grau

OBJECTIVES Prior studies have found that cardiac surgery patients receiving blood transfusions are at risk for increased mortality and morbidity following surgery. It is not clear whether this increased risk occurs across all haematocrit (HCT) levels. The goal of this study was to compare operative mortality in propensity-matched cardiac surgery patients based on stratification of the preoperative HCT levels. METHODS Between 1 August 2004 and 30 June 2011, 3516 patients had cardiac surgery. One thousand nine hundred and twenty-two (54.5%) required blood transfusion during or after surgery. A propensity score for transfusion was developed based on 22 baseline variables. One thousand seven hundred and fourteen patients were matched: 857 in the transfusion group (TG) and 857 in the non-transfused control group (CG). Univariate analyses demonstrated that, after propensity matching, the groups did not differ on any baseline factors included in the propensity model. Operative mortality was defined as death within 30 days of surgery. Preoperative HCT was stratified into four groups: <36, 36-39, 40-42 and ≥ 43. RESULTS For HCT <36%, 30-day mortality was higher in the TG than that in the CG (3.0 vs 0.0%). For HCT 36-39, operative mortality was similar between TG (1.1%, N = 180) and CG (0.8%, N = 361; P = 0.748). For HCT 40-42, operative mortality was significantly higher in the TG compared with that in the CG (1.9 vs 0%, N = 108 and 218, respectively; P = 0.044). For HCT of ≥ 43, there was a trend towards higher operative mortality in the TG vs the CG (2.0 vs 0%, N = 102 and 152, respectively; P = 0.083). Other surgical complications followed the same pattern with higher rates found in the transfused group at higher presurgery HCT levels. HCT at discharge for the eight groups were similar, with an average of 29.1 ± 1.1% (P = 0.117). CONCLUSIONS Our study indicates that a broad application of blood products shows no discernible benefits. Furthermore, patients who receive blood at all HCT levels may be placed at an increased risk of operative mortality and/or other surgical complications. Paradoxically, even though patients with low HCTs theoretically should benefit the most, transfusion was still associated with a higher complication and mortality rate in these patients. Our results indicate that blood transfusion should be used judiciously in cardiac surgery patients.


The Journal of Thoracic and Cardiovascular Surgery | 2015

Impact of pump status and conduit choice in coronary artery bypass: A 15-year follow-up study in 1412 propensity-matched patients

Juan B. Grau; Christopher K. Johnson; Cyrus E. Kuschner; Giovanni Ferrari; Richard E. Shaw; Mariano E. Brizzio; Alex Zapolanski

OBJECTIVE Previous studies have demonstrated that bilateral internal mammary artery (BIMA) grafts lead to superior outcomes compared with single internal mammary artery grafts. This study examines whether cardiopulmonary bypass affects conduit-dependent outcomes of coronary artery bypass grafting (CABG) surgery. METHODS From 1994 to 2013, a total of 6666 patients underwent isolated CABG surgery at our institution. Of these procedures, 3548 (53.2%) were performed off pump. A BIMA-saphenous vein graft (SVG) was used in 1544, and 5122 had left internal mammary artery-SVGs. These 2 conduit groups differed significantly in baseline characteristics. Propensity matching based on 22 preoperative variables and using a nearest-neighbor matching algorithm was used to make balanced cohorts, resulting in 2 groups of 1006. To account for the influence of pump status on conduit selection, a second propensity score was developed for pump use. These cases were matched to create 4 patient cohorts of 353 patients each (a total of 1412), balanced for both conduit use and pump status. Late mortality was determined using the Social Security Death Index. RESULTS No difference was found in survival between patients receiving BIMA-SVGs on or off pump (78.9% vs 79.1%). BIMA-SVGs outperformed the left internal mammary artery-SVGs regardless of whether the procedure was performed off pump (73.9%) or on pump (69.9%). CONCLUSIONS This study demonstrates that the use of cardiopulmonary bypass does not significantly affect the long-term outcomes in these patients as long as full revascularization is achieved. In addition, these results are consistent with prior research showing that the use of BIMAs produces better outcomes than use of a single internal mammary artery when performing CABG.


Interactive Cardiovascular and Thoracic Surgery | 2012

Impact of New York Heart Association classification, advanced age and patient-prosthesis mismatch on outcomes in aortic valve replacement surgery

Alex Zapolanski; Andrew W.C. Mak; Giovanni Ferrari; Christopher K. Johnson; Richard E. Shaw; Mariano E. Brizzio; Jason S. Sperling; Juan B. Grau

OBJECTIVES More elderly patients (>80 years of age) are being referred for aortic valve replacement (AVR) with or without CABG. Current risk stratification models may not accurately predict the preoperative risk in these patients. We sought to determine which perioperative variables were relevant in determining short-term (30-day to in-hospital) outcomes in our intuitions series of consecutive AVR and AVR+CABG surgeries. We constructed a novel variable, patient-prosthesis mismatch (PPM) in the presence of diminished functional status (NYHA) classification, and studied its role as a predictor of mortality risk. METHODS From 2006 to 2010, 509 patients undergoing AVR or AVR+CABG were evaluated. We created four groups based on the age and procedure (AVR >80, AVR+CABG >80, AVR <80 and AVR+CABG <80). PPM was defined as a calculated effective orifice area index value of ≤ 0.85, and it was calculated from manufacturer-generated charts. In-hospital and 30-day outcomes were assessed using the Chi-square and logistic regression analyses. RESULTS Overall observed 30-day mortality for all groups was lower (n = 8, 1.6%) than the STS-predicted mortality. Reoperation and PPM+NYHA class III-IV were associated with short-term mortality, but age >80 years was not. Octogenarians referred for surgery often had advanced heart failure. CONCLUSIONS Overall, short-term outcomes after AVR with or without CABG were excellent and lower than predicted by the STS model. The low risk of AVR with CABG supports the consideration for earlier surgical referral and intervention for patients with a high likelihood of aortic stenosis progression before the onset of advanced heart failure ensues, regardless of the age. This should help further decrease the already very low mortality observed in these series. Efforts to avoid PPM in the setting of advanced heart failure may improve short-term results in this subset of patients.


Genomics | 2014

Comparative genome-wide transcriptional analysis of human left and right internal mammary arteries

Giovanni Ferrari; John Quackenbush; John Strobeck; Lan Hu; Christopher K. Johnson; Andrew W.C. Mak; Richard E. Shaw; Kathleen Sayles; Mariano E. Brizzio; Alex Zapolanski; Juan B. Grau

In coronary artery bypass grafting (CABG), the combined use of left and right internal mammary arteries (LIMA and RIMA) - collectively known as bilateral IMAs (BIMAs) provides a survival advantage over the use of LIMA alone. However, gene expression in RIMA has never been compared to that in LIMA. Here we report a genome-wide transcriptional analysis of BIMA to investigate the expression profiles of these conduits in patients undergoing CABG. As expected, in comparing the BIMAs to the aorta, we found differences in pathways and processes associated with atherosclerosis, inflammation, and cell signaling - pathways which provide biological support for the observation that BIMA grafts deliver long-term benefits to the patients and protect against continued atherosclerosis. These data support the widespread use of BIMAs as the preferred conduits in CABG.


Insulin | 2009

When a unit of insulin is not a unit: Detemir dosing and insulin cost in type 2 diabetes mellitus

Christopher K. Johnson; Mona Shimshi

Abstract Background: Increasing acceptance of basal-bolus insulin therapy for the control of diabetes mellitus (DM) has led to newer formulations of basal insulin analogues. The newest one is detemir. Objectives: Clinical evidence suggests that patients with type 2 DM require higher doses of detemir than other basal insulins to achieve equivalent glycemic control. This study examines evidence for greater dosing requirements and the implications of higher doses on the cost of insulin treatment. Methods: We performed a MEDLINE search for randomized, prospective studies comparing detemir with other basal insulins in patients with type 2 DM that were published in English between January 2000 and November 2008. The mean daily doses of basal and bolus insulin and the mean total daily insulin doses were determined. Overall weighted mean doses of the insulins were used to estimate the mean total daily insulin doses required for a 100-kg patient, and published 2008 US retail prices were used to estimate the retail costs of basal-bolus and basal-only insulin regimens. Results: Seven trials involving 3311 patients were identified in the literature search. The mean total daily insulin dose was 0.80 unit/kg for detemir-based regimens and 0.58 unit/kg for comparison regimens. For basal-bolus regimens, the estimated retail cost of the mean total daily insulin dose was


Cardiovascular Pathology | 2014

Intracardiac juvenile xanthogranuloma with presentation in adulthood.

Heidi D. Lehrke; Christopher K. Johnson; Alex Zapolanski; Alex Kasatki; Juan B. Grau; Joseph J. Maleszewski

11.24 for detemir-based regimens compared with

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Juan B. Grau

University of Pennsylvania

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Richard E. Shaw

California Pacific Medical Center

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Giovanni Ferrari

University of Pennsylvania

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