Spencer J Melby

University of Washington Seattle, Seattle, WA, United States

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Publications (39)90.19 Total impact

  • Annual Meeting Society of Free Radical Biology and Medicine 2013; 11/2013
  • 20th Annual Meeting of Society for Free Radical Biology and Medicine; 11/2013
  • 20th Annual Meeting of the Society for Free Radical Biology and Medicine; 11/2013
  • 20th Annual Meeting of Society for Free Radical Biology and Medicine; 11/2013
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    ABSTRACT: The purpose of this study was to evaluate factors that impact outcome following repair of type A aortic dissection. Over 25 years (1984-2009), 252 patients underwent repair of acute type A dissection. Mean follow-up for reoperation or death was 6.9±5.9 years. Operative mortality was 16% (41 of 252). Multivariate analysis identified one risk factor for operative death: presentation malperfusion (P=.003). For operative survivors, 5-, 10-, and 20-year survival was 78%±3%, 59%±4%, and 24%±6%, respectively. Late death occurred earlier in patients with previous stroke (P=.02) and chronic renal insufficiency (P=.007). Risk factors for late reoperation included male sex (P=.006), Marfan syndrome (P<.001), elevated systolic blood pressure (SBP, P<.001), and absence of β-blocker therapy (P<.001). Kaplan-Meier analysis demonstrated at 10-year follow-up that patients who maintained SBP <120 mm Hg had improved freedom from reoperation (92±5%) compared with those with SBP 120 mm Hg to 140 mm Hg (74%±7%) or >140 mm Hg (49%±14%, P<.001). At 10-year follow-up, patients on β-blocker therapy experienced 86%±5% freedom from reoperation compared with only 57%±11% for those without (P<.001). Operative survival was decreased with preoperative malperfusion. Long-term survival was dependent on comorbidities but not operative approach. Reoperation was markedly increased in patients not on β-blocker therapy and decreased with improved SBP control. Strict control of hypertension with β-blocker therapy is warranted following repair of acute type A dissection.
    Journal of Clinical Hypertension 01/2013; 15(1):63-8. · 2.36 Impact Factor
  • 19t Annual Meeting of the Society for Free Radical Biology and Medicine; 11/2012
  • The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation 08/2012; 31(8):903-4. · 3.54 Impact Factor
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    ABSTRACT: The presence of pulmonary hypertension historically has been considered a significant risk factor affecting early and late outcomes after valve replacement. Given the number of recent advances in the management of pulmonary hypertension after cardiac surgery, a better understanding of its impact on outcomes may assist in the clinical management of these patients. The purpose of this study was to determine whether pulmonary hypertension remains a risk factor in the modern era for adverse outcomes after aortic valve replacement for aortic valve stenosis. From January 1996 to June 2009, a total of 1080 patients underwent aortic valve replacement for primary aortic valve stenosis, of whom 574 (53%) had normal systolic pulmonary artery pressures (sPAP) and 506 (47%) had pulmonary hypertension. Pulmonary hypertension was defined as mild (sPAP 35-44 mm Hg), moderate (45-59 mm Hg), or severe (≥ 60 mm Hg). In the group of patients with pulmonary hypertension, 204 had postoperative echocardiograms. Operative mortality was significantly higher in patients with pulmonary hypertension (47/506, 9%, vs 31/574, 5%, P = .02). The incidence of postoperative stroke was similar (P = .14), but patients with pulmonary hypertension had an increased median hospital length of stay (8 vs 7 days, P = .001) and an increased incidence of prolonged ventilation (26% vs 17%, P < .001). Preoperative pulmonary hypertension was an independent risk factor for decreased long-term survival (relative risk 1.7, P = .02). Those with persistent pulmonary hypertension postoperatively had decreased survival. Five-year survival (Kaplan-Meier) was 78% ± 6% with normal sPAP and 77% ± 7% with mild pulmonary hypertension postoperatively, compared with 64% ± 8% with moderate and 45% ± 12% with severe pulmonary hypertension (P < .001). In patients undergoing aortic valve replacement, preoperative pulmonary hypertension increased operative mortality and decreased long-term survival. Patients with persistent moderate or severe pulmonary hypertension after aortic valve replacement had decreased long-term survival. These data suggest that pulmonary hypertension had a significant impact on outcomes in patients undergoing aortic valve replacement and should be considered in preoperative risk assessment.
    The Journal of thoracic and cardiovascular surgery 06/2011; 141(6):1424-30. · 3.41 Impact Factor
  • The Journal of thoracic and cardiovascular surgery 09/2010; 140(3):e56-8. · 3.41 Impact Factor
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    ABSTRACT: Lung transplantation for end-stage chronic obstructive lung disease is now considered the standard of care. We report a case of perioperative myocardial ischemia and cardiovascular compromise in a single lung transplant recipient due to right coronary artery occlusion from mediastinal shift and repositioning of the heart.
    The Annals of thoracic surgery 06/2010; 89(6):2000-1. · 3.45 Impact Factor
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    ABSTRACT: The Cox maze procedure is an effective treatment of atrial fibrillation, with a long-term freedom from recurrence greater than 90%. The original procedure was highly invasive and required cardiopulmonary bypass. Modifications of the procedure that eliminate the need for cardiopulmonary bypass have been proposed, including use of alternative energy sources to replace cut-and-sew lesions with lines of ablation made from the epicardium on the beating heart. This has been challenging because atrial wall muscle thickness is extremely variable, and the muscle can be covered with an epicardial layer of fat. Moreover, the circulating intracavitary blood acts as a potential heat sink, making transmural lesions difficult to obtain. In this report, we summarize the use of nine different unidirectional devices (four radiofrequency, two microwave, two lasers, one cryothermic) for creating continuous transmural lines of ablation from the atrial epicardium in a porcine model. We define a unidirectional device as one in which all the energy is applied by a single transducer on a single heart surface. The maximum penetration of any device was 8.3 mm. All devices except one, the AtriCure Isolator pen, failed to penetrate 2 mm in some nontransmural sections. Future development of unidirectional energy sources should be directed at increasing the maximum depth and the consistency of penetration.
    Heart rhythm: the official journal of the Heart Rhythm Society 12/2009; 6(12 Suppl):S41-5. · 4.56 Impact Factor
  • Spencer J Melby, Sanjiv K Gandhi
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    ABSTRACT: Aortopulmonary window is a rare abnormal congenital communication between the pulmonary artery and the ascending aorta with intact aortic and pulmonary valves. Because pulmonary hypertension and premature death are the natural history of the uncorrected left-to-right shunt physiology that occurs with aortopulmonary window, surgical correction, which is the gold standard of treatment, should be offered to patients at the time of diagnosis, before the development of lung injury and irreversible pulmonary hypertension.
    Current Treatment Options in Cardiovascular Medicine 10/2009; 11(5):392-5.
  • Anson M Lee, Spencer J Melby, Ralph J Damiano
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    ABSTRACT: Atrial fibrillation is a complex disease affecting a significant portion of the general population. Although medical therapy is the mainstay of treatment, intervention plays an important role in selected patients. The Cox-Maze procedure is the gold standard for the surgical treatment of atrial fibrillation and has more than 90% success in eliminating atrial fibrillation. Ablation technologies have played a key role in simplifying this technically demanding procedure and making it available to more patients. A myriad of new lesion sets and approaches were introduced over the last decade which has made the operative treatment of atrial fibrillation less invasive and more confusing.
    Surgical Clinics of North America 08/2009; 89(4):1001-20, x-xi. · 2.02 Impact Factor
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    ABSTRACT: Patients with chronic pulmonary hypertension (CPH) who demonstrate pulmonary vasodilation following calcium-channel blocker (CCB) administration are defined as 'responders'. In contrast, 'nonresponders' are patients who do not show such pulmonary vasodilation with CCB therapy. The purpose of this investigation was to study the effects of CCB therapy on right heart mechanics in experimental CCB responders versus CCB nonresponders. In 12 dogs, right atrial (RA) and ventricular pressure and volume (conductance catheters) were simultaneously recorded after 3 months of progressive pulmonary artery banding. Diltiazem was given at 10 mg h with the pulmonary artery constricted (simulated CCB nonresponder). Responders were then created by releasing the pulmonary artery band to unload the ventricle. RA and right ventricular contractility and diastolic stiffness (slope of end-systolic and end-diastolic pressure-volume relations) were calculated and RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed compared with open, respectively. With CCB, RA contractility (P < 0.03) and cardiac output (P < 0.004) were compromised in simulated nonresponders whereas RA stroke work was pharmacologically depressed in the setting of an unchanged afterload. After simulating a responder by controlled pulmonary artery band release, the right atrium became less distensible, causing a shift from reservoir to conduit function (P < 0.001) towards physiological baseline conditions and a recovery in the hyperdynamic compensatory response in both chambers (P < 0.007) as evidenced by declined RA and right ventricular contractility with an improved cardiac output as compared with CPH and simulated nonresponders. RA and right ventricular diastolic function in both groups was not affected by CCB. CCB did not affect right ventricular function in simulated nonresponders but significantly impaired RA contractility and cardiac output. In simulated responders, afterload fell substantially, thereby allowing the right atrium and right ventricle to recover from their pathological hyperdynamic contractile response to CPH. This effect outweighed the intrinsic negative effects of CCB therapy on systolic RA function. Current data suggest that the right atrium in CPH is much more sensitive to CCB therapy than the right ventricle and show for the first time why CCB therapy in CPH has been empirically restricted to documented responders.
    European Journal of Anaesthesiology 04/2009; 26(3):253-9. · 2.79 Impact Factor
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    ABSTRACT: The purpose of the present study was to determine for the first time the qualitative and quantitative impact of varying degrees of interatrial shunting on right heart dynamics and systemic perfusion in subjects with chronic pulmonary hypertension (CPH). Eight dogs underwent 3 mo of progressive pulmonary artery banding, following which right atrial and ventricular end-systolic and end-diastolic pressure-volume relations were calculated using conductance catheters. An 8-mm shunt prosthesis was inserted between the superior vena cava and left atrium, yielding a controlled model of atrial septostomy. Data were obtained 1) preshunt or "CPH"; 2) "Low-Flow" shunt; and 3) "High-Flow" shunt (occluding superior vena cava forcing all flow through the shunt). With progressive shunting, right ventricular pressure fell from 72 +/- 19 mmHg (CPH) to 54 +/- 17 mmHg (Low-Flow) and 47 +/- 17 mmHg (High-Flow) (P < 0.001). Cardiac output increased from 1.5 +/- 0.3 l/min at CPH to 1.8 +/- 0.4 l/min at Low-Flow (286 +/- 105 ml/min, 15% of cardiac output; P < 0.001), but returned to 1.6 +/- 0.3 l/min at High-Flow (466 +/- 172 ml/min, 29% of cardiac output; P = 0.008 vs. Low-Flow, P = 0.21 vs. CPH). There was a modest rise in systemic oxygen delivery from 252 +/- 46 ml/min at CPH to 276 +/- 50 ml/min at Low-Flow (P = 0.07), but substantial fall to 222 +/- 50 ml/min at High-Flow (P = 0.005 vs. CPH, P < 0.001 vs. Low-Flow). With progressive shunting, bichamber contractility did not change (P = 0.98), but the slope of the right atrial end-diastolic pressure volume relation decreased (P < 0.04), consistent with improved compliance. This study demonstrated that Low-Flow interatrial shunting consistently improved right atrial mechanics and systemic perfusion in subjects with CPH, while High-Flow exceeded an "ideal shunt fraction".
    AJP Heart and Circulatory Physiology 02/2009; 296(3):H639-44. · 3.63 Impact Factor
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    ABSTRACT: The introduction of ablation technology has simplified surgical intervention for atrial fibrillation. However, most ablation devices cannot create focal transmural lesions on the beating heart and have difficulty ablating specific regions of the atria, such as the atrioventricular isthmus, coronary sinus, and ganglionated plexus. The purpose of this study was to examine the efficacy of a pen-type bipolar radiofrequency ablation device on both arrested and beating hearts. Endocardial and epicardial atrial tissues in the free wall, left atrial roof, atrioventricular annuli, and coronary sinus were ablated for varying time intervals (2.5-15 seconds) in porcine cardioplegically arrested (n = 6) and beating (n = 9) hearts. The hearts were stained with 1% 2,3,5-triphenyl-tetrazolium chloride solution and sectioned to determine lesion depth and width. In 5 animals epicardial fat pads containing ganglionated plexus were stimulated and ablated. Lesion depth increased with ablation time similarly in both arrested and beating hearts. Transmurality was fully achieved in the thin atrial tissue (<4 mm) at 10 seconds in the beating and arrested hearts. The device had a maximal penetration depth of 6.1 mm. Epicardial ablation of the coronary sinus showed complete penetration through the left posterior atrium only in the arrested heart. Seven of 17 fat pads demonstrated a vagal response. All vagal responses were eliminated after ablation. The bipolar pen effectively ablated atrial tissue in both arrested and beating hearts. This device might allow the surgeon to ablate tissue in regions not accessible to other devices during atrial fibrillation surgery.
    The Journal of thoracic and cardiovascular surgery 12/2008; 136(5):1295-301. · 3.41 Impact Factor
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    ABSTRACT: It has been hypothesized that atrial lesions must be transmural to successfully cure atrial fibrillation (AF). However, ablation lines often do not extend completely across the atrial wall. The purpose of this study was to determine the effect of residual gaps on conduction properties of atrial tissue. Canine right atria (n = 13) were isolated, perfused, and mounted on a 250-lead electrode plaque. The atria were divided with a bipolar radiofrequency ablation clamp, leaving a gap that was progressively narrowed. Conduction velocities at varying pacing rates and AF frequencies were measured before and after ablations. AF was induced with an extra stimulus and acetylcholine. Gap widths from 11.2 to 1.1 mm were examined. Conduction velocities through gaps were dependent cycle length (P = .002) and gap size (P <.001). Overall, 253 (97%) of a total of 260 gaps allowed paced propagation; 51 (91%) of 56 gaps 1-3 mm in width permitted paced propagation, as did 202 (99%) of 204 gaps >or=3.0 mm. Similarly, 253 (97%) of a total of 260 gaps allowed propagation of AF. For AF, 51 (93%) of 55 gaps 1-3 mm allowed AF to pass through, as did 202 (99%) of 205 gaps >or=3.0 mm. Gaps as small as 1.1 mm conducted paced and AF impulses. Conduction velocities were slowed through residual gaps. However, propagation of wave fronts during pacing and AF occurred through the majority of residual gaps, down to sizes as small as 1.1 mm. Leaving viable tissue in ablation lines for the treatment of AF could account for failures.
    Heart rhythm: the official journal of the Heart Rhythm Society 09/2008; 5(9):1296-301. · 4.56 Impact Factor
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    ABSTRACT: BACKGROUND/OBJECTIVE: Atrial fibrillation(AF) has been shown in numerous studies to significantly decrease patient quality of life. The Cox-Maze procedure has excellent long-term efficacy in curing AF. However, it is unknown whether this procedure improves long-term quality of life in these patients. The purpose of this study was to examine late quality of life in patients that underwent a lone Cox-Maze procedure. METHODS: Between 1987 and 2003, 163 patients underwent a Cox-Maze procedure for lone AF at our institution. Of these, 68 patients agreed and completed the Medical Outcomes Study Short Form 36 Health Survey. Scores from the age-matched general US population were normalized to a mean of 50 and standard deviation of 10 to facilitate comparison. Collected data were compared to the norm-based score for each domain using a one-sample t-test. Four patients were removed from analysis because of AF recurrence. RESULTS: There were 52 males(81%). Mean age was 52.6±9.5 years. Preoperatively, 37 patients(58%) had paroxysmal and 25 patients(39%) had persistent or permanent AF. The mean duration of AF before surgery was 9.8±8.2 years. There was no statistical difference in norm-based scores between the Cox-Maze procedure group and the age-matched general US population in any of the eight health domains at a mean follow-up of 8.7±3.7 years. CONCLUSION: Our results suggest that the Cox-Maze procedure cures atrial fibrillation in the majority of patients, and that those patients that are cured obtain a normal quality of life as compared to the general population at late follow-up.
    Innovations Technology and Techniques in Cardiothoracic and Vascular Surgery 05/2008; 3(3):142-146.
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    ABSTRACT: The results of treatment for subclavian vein effort thrombosis were assessed in a series of competitive athletes. A retrospective review was conducted of high-performance athletes who underwent multidisciplinary management for venous thoracic outlet syndrome in a specialized referral center. The overall time required to return to athletic activity was assessed with respect to the timing and methods of diagnosis, initial treatment, operative management, and postoperative care. Between January 1997 and January 2007, 32 competitive athletes (29 male and 3 female) were treated for venous thoracic outlet syndrome, of which 31% were in high school, 47% were in college, and 22% were professional. The median age was 20.3 years (range, 16-26 years). Venous duplex ultrasound examination in 21 patients had a diagnostic sensitivity of 71%, and the mean interval between symptoms and definitive venographic diagnosis was 20.2 +/- 5.6 days (range, 1-120 days). Catheter-directed subclavian vein thrombolysis was performed in 26 (81%), with balloon angioplasty in 12 and stent placement in one. Paraclavicular thoracic outlet decompression was performed with circumferential external venolysis alone (56%) or direct axillary-subclavian vein reconstruction (44%), using saphenous vein panel graft bypass (n = 8), reversed saphenous vein graft bypass (n = 3), and saphenous vein patch angioplasty (n = 3). In 19 patients (59%), simultaneous creation of a temporary (12 weeks) adjunctive radiocephalic arteriovenous fistula was done. The mean hospital stay was 5.2 +/- 0.4 days (range, 2-11 days). Seven patients required secondary procedures. Anticoagulation was maintained for 12 weeks. All 32 patients resumed unrestricted use of the upper extremity, with a median interval of 3.5 months between operation and the return to participation in competitive athletics (range, 2-10 months). The overall duration of management from symptoms to full athletic activity was significantly correlated with the time interval from venographic diagnosis to operation (r = 0.820, P < .001) and was longer in patients with persistent symptoms (P < .05) or rethrombosis before referral (P < .01). Successful outcomes were achieved for the management of effort thrombosis in a series of 32 competitive athletes using a multidisciplinary approach based on (1) early diagnostic venography, thrombolysis, and tertiary referral; (2) paraclavicular thoracic outlet decompression with external venolysis and frequent use of subclavian vein reconstruction; and (3) temporary postoperative anticoagulation, with or without an adjunctive arteriovenous fistula. Optimal outcomes for venous thoracic outlet syndrome depend on early recognition by treating physicians and prompt referral for comprehensive surgical management.
    Journal of Vascular Surgery 04/2008; 47(4):809-820; discussion 821. · 2.88 Impact Factor
  • Thoracic and Cardiovascular Surgeon - THORAC CARDIOVASC SURG. 01/2008; 56.