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Biomedical subjects

Marc R Moon

Publications and source records attributed to Marc R Moon.

At least 37 records · Page 2Linked to original sources
PubMed2004

Mechanical support for isolated right ventricular failure in patients after cardiotomy.

BACKGROUND: Patients with acute right ventricular (RV) failure after cardiotomy have a poor prognosis. We evaluated the surgical and long-term outcomes of patients with isolated RV failure that required right ventricular assist device (RVAD) support. METHODS: Between 1991 and 2002, a total of 30 patients received RVAD support for isolated RV dysfunction. We evaluated survival, duration of mechanical support, post-RVAD hemodynamics, and RV function. RESULTS: Right ventricular failure developed in patients after coronary artery bypass surgery alone or combined with valve surgery (12 patients), valvular surgery (5), ascending aortic replacement (6), heart transplantation (3), and pulmonary endarterectomy (4). Mean age was 58 +/- 15 years, and 17 (57%) were women. Surgery was emergent in 5 (73%) patients. Centrifugal pumps were used in 21, extra corporeal membrane oxygenation in 8, and as Abiomed pump in 1 patient. Overall, 17 (57%) patients died while receiving assist device support, 3 of sepsis, 2 of stroke, and 12 of inability to wean from the device. We successfully weaned RVAD support in 13 (43%) patients, with a median duration of support of 5 days (range, 2-8 days). Ten survived to hospital discharge. After RVAD removal, mean pulmonary artery pressure was 25.1 +/- 6.5 mmHg, cardiac output was 4.8 +/- 2.0 liters, and central venous pressure was 16.5 +/- 3.7 mmHg. Echocardiogram after RVAD removal showed normal RV function in 2 patients and in 11 patients demonstrated improvement. CONCLUSION: After cardiotomy, patients with RV failure who require mechanical support continue to have increased mortality. For patients successfully weaned from the RVAD, residual RV dysfunction is compatible with survival. More liberal use of RV mechanical support may be indicated for patients with acute RV failure.

Cardiac Output, Low↗
PubMed2004

A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation.

OBJECTIVE: The Cox maze III procedure has excellent long-term efficacy in curing atrial fibrillation. It has not been widely practiced because it is technically challenging and requires prolonged cardiopulmonary bypass. The aim of this study was to examine a simplified Cox maze III procedure that uses bipolar radiofrequency energy as an ablative source. METHODS: Beginning January 2002, a total of 40 consecutive patients underwent a modified Cox maze III procedure with bipolar radiofrequency energy. Nineteen had a lone maze procedure and 21 had a maze procedure plus a concomitant operation. One month after the operation, the first 8 patients were investigated with high-resolution magnetic resonance imaging. Patients were followed up monthly with clinical examination and electrocardiography. RESULTS: There was no operative deaths. The crossclamp times were 47 +/- 26 minutes for the modified lone Cox maze III procedure and 92 +/- 37 minutes for the Cox maze III procedure plus concomitant procedures. These were significantly shorter than our previous times for the traditional Cox maze III procedure (93 +/- 34 minutes and 122 +/- 37 minutes, respectively, P <.05). Follow-up magnetic resonance imaging showed no evidence of pulmonary vein stenosis, and atrial contractility was preserved in all patients. There were no late strokes. At 6-month follow-up, 91% of patients (21/23) were in sinus rhythm. CONCLUSIONS: Bipolar radiofrequency ablation can be used to replace the surgical incisions of the Cox maze procedure. This energy source did not result in pulmonary vein stenosis. The modification of the Cox maze III procedure to use bipolar radiofrequency ablation simplified and shortened this procedure without sacrificing short-term efficacy.

Atrial Fibrillation↗
PubMed2003

Delayed paraplegia after thoracic and thoracoabdominal aneurysm repair: a continuing risk.

BACKGROUND: Paraplegia or paraparesis after otherwise successful thoracic or thoracoabdominal aortic reconstruction is a devastating complication for patient and physician. Interventions for its prevention have focused primarily on the intraoperative period. We have recently noted a significant incidence of delayed-onset neurologic deficit. METHODS: We reviewed our most recent 5-year experience with thoracic and thoracoabdominal reconstruction to examine the incidence of and potential contributors to delayed paraplegia or paraparesis. RESULTS: Between June 1996 and June 2001, 60 patients (29 men, 31 women) underwent repair of isolated thoracic (n = 26) or thoracoabdominal aortic aneurysm (Crawford I, n = 7; Crawford II, n = 14; Crawford III, n = 12; Crawford IV, n = 1) by the cardiac and vascular surgical services collaboratively. Repair was performed endovascularly in 6, and open with either circulatory arrest in 12, partial left heart bypass in 37, or partial femorofemoral bypass in 5. Operative mortality was 9.3% (5 of 54 patients) for open repair and 0% for endovascular repair. Paraplegia or paraparesis occurred in 6 (10%) patients of which 83.3% (5 of 6) were delayed in onset. All patients with delayed paraplegia or paraparesis had degenerative aneurysms of Crawford extent II (n = 3) or III (n = 2), had intraoperative left heart bypass, and had perioperative spinal drainage. Delayed paraplegia or paraparesis occurred up to 27 days postoperatively, and was associated with a documented episode of hypotension in 60% (3 of 5) of patients. CONCLUSIONS: Improvements in intraoperative management may have reduced immediate paraplegia or paraparesis among vulnerable patients only to leave them at risk of delayed-onset deficit. Postoperative care, including assiduous attention to avoidance of even transient hypotension, must be tailored to this patient population.

Adult↗
PubMed2003

Effect of a cardiac-specific didactic course on thoracic surgery in-training examination performance.

BACKGROUND: The purpose of this study was to determine which factors influenced performance on the Thoracic Surgery In-Training Examination (TSITE) and whether the addition of a cardiac-specific didactic study course improved scores. METHODS: Between 1989 and 2002, 59 TSITE scores (overall, cardiac [C-TSITE], and thoracic [T-TSITE]) were collected from 33 residents (23 cardiac track, 10 thoracic). Factors assessed with univariate and multivariate analysis included calendar year, year of training (31 year I, 28 year II), standardized test-taking history (average National Board and American Board of Surgery in-training scores), subjective faculty assessment of cardiothoracic knowledge, months on cardiac versus thoracic service, clinical performance, and participation in a cardiac-specific didactic series with faculty lectures and board question reviews (12 residents). RESULTS: Cardiac-track residents had higher C-TSITE percentile scores (53% +/- 27% versus 38% +/- 27%, p < 0.05), whereas thoracic-track residents had higher T-TSITE scores (70% +/- 24% versus 51% +/- 25%, p < 0.01). Multivariate analysis identified 3 factors associated with higher overall TSITE scores: standardized test-taking history (p < 0.001), subjective faculty assessment of knowledge (p < 0.001), and year of training (p < 0.007). Inclusion in the cardiac-specific didactic series did not affect C-TSITE scores (50% +/- 30% versus 48% +/- 27%, p > 0.82) or overall TSITE scores (p > 0.23). CONCLUSIONS: Standardized test-taking history and subjective faculty assessment of knowledge were associated with higher TSITE scores, but implementation of a cardiac-specific didactic series had no influence. These findings suggest that independent study and reading may be the best way to improve TSITE scores.

Educational Measurement↗
PubMed2003

Nesiritide (BNP) in the management of postoperative cardiac patients.

Recombinant human B-type natriuretic peptide (BNP) is a promising new agent in the management of heart failure. The pharmacologic properties of BNP make it desirable to use in a subset of patients after cardiac surgical operations. Among these therapeutic potentials is the effect on markedly reducing pulmonary vascular resistance and central venous pressure with mild systemic vasodilatation. In addition, BNP directly effects the kidneys to promote natriuresis. We believe this agent to be useful in the treatment of the postcardiac surgery patients with left ventricular dysfunction and mild to moderate renal insufficiency. This report summarizes our experience in 2 patients.

Aged↗
PubMed2003

Quality of life and survival after transmyocardial laser revascularization with the holmium:YAG laser.

BACKGROUND: The purpose of this investigation was to assess postoperative survival and quality of life with transmyocardial laser revascularization (TMR) in high-risk patients. METHODS: During a 24-month period, 81 consecutive patients underwent either sole therapy TMR (n = 34) or TMR with coronary artery bypass grafting (n = 47) using a holmium:yttrium-aluminum-garnet (YAG) laser. Outcomes were assessed in three high-risk groups, including patients with left ventricular dysfunction (ejection fraction < or = 0.40) (n = 37), unstable angina (n = 30), and congestive heart failure (n = 33). Disease-specific quality of life was assessed using the Seattle Angina Questionnaire in 58 late survivors and compared with an age-matched cohort undergoing coronary artery bypass grafting only (no TMR) (n = 20). RESULTS: Overall mortality was 6% +/- 3% (+/- 70% confidence limit) and appeared higher with left ventricular dysfunction (11% +/- 5% vs 2% +/- 2%), but the difference did not reach statistical significance (p = 0.17; power = 0.16). There was also no statistical difference with unstable angina (10% +/- 6% vs 4% +/- 3%; p > 0.53) or congestive failure (9% +/- 5% vs 4% +/- 3%; p > 0.66). However, survival at 18 months was significantly lower with left ventricular dysfunction (62% +/- 9% vs 90% +/- 5%; p < 0.003) and congestive failure (48% +/- 10% vs 96% +/- 3%; p < 0.001). For sole therapy TMR, quality of life was diminished comparing TMR with coronary artery bypass grafting (p < 0.004) and coronary artery bypass grafting only (p < 0.002). CONCLUSIONS: Transmyocardial laser revascularization can be performed in high-risk patients, but survival is significantly impaired in patients with left ventricular dysfunction and congestive failure, and quality of life is diminished without some degree of direct revascularization.

Adult↗
PubMed2003

Radial artery patency: are aortocoronary conduits superior to composite grafting?

BACKGROUND: The radial artery (RA) can be used as either an aortocoronary (RA-Ao) or composite graft (T graft). Optimum use for the RA has yet to be established. We compared RA patency with these two techniques. METHODS: Between October 1993 and June 2001, 1505 patients underwent coronary artery bypass grafting using the RA as either a composite (n = 1022) or RA-Ao graft (n = 483). Angiograms performed on 203 (13.5%) patients with signs or symptoms of ischemia at an average of 26.1 +/- 18.5 months postoperatively were reviewed. RESULTS: Patients with RA-Ao grafts had a greater incidence of postoperative angiography versus patients with composite grafts (19% versus 11%; p < 0.01). Patients receiving T grafts had a greater number of anastomoses per patient (4.1 +/- 0.6 versus 3.0 +/- 1.0; p < 0.01) and a higher incidence of total arterial revascularization (100% versus 41%; p < 0.01). Regardless of grafting strategy, patency was significantly worse for targets of the right coronary artery (58% T graft; 67% RA-Ao; p < 0.01 for both) and for targets with less than or equal to 70% stenosis (59% T graft; 57% RA-Ao; p < 0.01 for both). The site of proximal anastomosis failed to effect RA patency (relative risk, 1.2; 95% confidence interval, 0.7 to 1.8; p = 0.50). CONCLUSIONS: The site of the proximal anastomosis does not appear to influence patency. Both RA-Ao and composite conduits are sensitive to target location and stenosis. Advantages of composite grafting include greater conduit length and minimizing aortic manipulation at the expense of increased complexity and the potential for hypoperfusion. These factors should be considered when choosing an RA grafting strategy.

Aged↗
PubMed2003

The influence of mechanical properties on wall stress and distensibility of the dilated ascending aorta.

OBJECTIVES: We sought to determine how intrinsic mechanical properties of dilated ascending aorta influence in vivo distensibility and wall stress, potential contributing factors to the risk of aortic rupture and dissection. METHODS: Fresh tissue from patients undergoing ascending aortic replacement for Marfan syndrome (n = 8, age 38 +/- 14 years), bicuspid aortic valve with associated aneurysm (n = 20, age 55 +/- 12 years), or idiopathic degenerative aneurysm (n = 7, age 64 +/- 9 years) was analyzed for elastic properties and circumferential residual stress. Histologic specimens were graded for elastin fragmentation, cystic changes, fibrosis, and necrosis. Distensibility and wall stresses were predicted with a cylindrical mathematical model of the aorta. RESULTS: Elastic properties of aortic tissue were nonlinear and extensibility decreased with age. Moderate or severe elastin fragmentation was prevalent in tissue from patients with the Marfan syndrome and more common in tissue from younger patients. Model-predicted mean circumferential stress did not vary significantly with age or patient group, but increased with aortic lumen diameter and systolic blood pressure. Model-predicted distensibility decreased with age in bicuspid aortic valve and degenerative aneurysm groups. Differences in distensibility were correlated with differences in elastic properties. CONCLUSIONS: The age dependence of elastic properties of dilated ascending aorta is consistent with that of normal aorta observed in previous studies. Increases in mean circumferential stress with blood pressure and diameter support the clinical importance of blood pressure control and serial evaluation of aortic diameter. Declining wall strength with age may increase the risk of rupture or dissection.

Adolescent↗
PubMed2003

Percutaneous management of ischemic complications in patients with type-B aortic dissection.

PURPOSE: To review our experience with the use of percutaneous methods to manage the ischemic complications of type-B aortic dissection. MATERIALS AND METHODS: Retrospective review of our interventional radiology database identified 11 patients with acute type-B aortic dissection who underwent 13 endovascular procedures to attempt revascularization of 23 ischemic vascular territories (four mesenteric, 11 renal, eight lower extremities). Percutaneous interventions included balloon fenestration (four patients), aortic true lumen stent placement (three patients), and branch vessel stent placement (eight patients). RESULTS: Successful initial reperfusion of 21 of 23 vascular territories (91%) was achieved with use of percutaneous methods alone, with no 30-day mortality, in-hospital mortality, or paraplegia. One additional patient underwent successful initial treatment with use of a combined interventional/surgical approach to reperfuse an ischemic limb. One patient developed acute thrombosis of a dissected renal artery during stent placement. Increased aortic true lumen collapse later resulted in further ischemia in two patients. During follow-up (mean, 16 mo), no patient has had evidence of false lumen enlargement or late recurrent ischemia. CONCLUSION: Endovascular methods offer a less-morbid nonsurgical treatment alternative for patients with acute complicated type-B aortic dissection.

Aortic Dissection↗
PubMed2002

Impact of pericardial restraint on right atrial mechanics during acute right ventricular pressure load.

Optimization of right atrial (RA) mechanics is important for maintaining right ventricular (RV) filling and global cardiac output. However, the impact of pericardial restraint on RA function and the compensatory role of the right atrium to changes in RV afterload remain poorly characterized. In eight open-chest sheep, RA elastance (contractility) and chamber stiffness were measured (RA pressure-volume relations) at baseline and during partial pulmonary artery (PA) occlusion. Data were collected before and after pericardiotomy. With the pericardium intact and partial PA occlusion, RA elastance increased by 28% (P < 0.04), whereas RA stiffness tended to rise (P = 0.08). However, after pericardiotomy, there was a significant fall in both RA elastance (54%, P < 0.04) and stiffness (39%, P < 0.04), and subsequent PA occlusion failed to induce a change in elastance (P > 0.19) or stiffness (P > 0.84). After pericardiotomy, RA elastance and stiffness fell dramatically, and the compensatory response of the right atrium to elevated RV afterload was lost. The ability of the right atrium to respond to changes in RV hemodynamics is highly dependent on pericardial integrity.

Animals↗
PubMed2002

Reoperative transmyocardial laser revascularization for late recurrent angina.

Transmyocardial laser revascularization (TMR) reduces anginal class and is indicated for severely symptomatic patients who are not candidates for conventional revascularization. This report describes a 72-year-old man who presented 4 years following initially successful TMR with recurrent angina refractory to maximal medical management. Reoperative TMR was performed with substantial improvement in angina and functional class.

Aged↗
PubMed2002

Laser-assist during extraction of chronically implanted pacemaker and defibrillator leads.

BACKGROUND: Extraction of chronically implanted pacing and defibrillator leads has historically been difficult, occasionally requiring open surgical procedures. The purpose of this study was to evaluate the efficacy, safety, and potential need for percutaneous laser-assisted sheath techniques for extraction of chronically implanted leads. METHODS: From January 1999 to August 2001, 128 consecutive patients underwent extraction of 229 leads (138 pacing, 91 defibrillator) in the operating room 61 +/- 44 (mean +/- standard deviation) months after implantation. Common indications included erosion or pocket infection (41%), lead dysfunction (30%), and sepsis (13%). RESULTS: Laser techniques were used for 56% +/- 4% (104 of 186) of long-term (implanted for more than 1 year) leads, compared with only 16% +/- 6% (7 of 43) of short-term (implanted for less than 1 year) leads (p < 0.001). For infected leads, laser was used in 53% +/- 5% (49 of 92) with erosion or pocket infections, compared with only 3% +/- 4% (1 of 29) with sepsis (p < 0.001). Extraction was complete in 88%, near complete (retained tip) in 10%, and incomplete in 2%. Two patients required a later percutaneous femoral venous approach to remove mobile retained segments, but no patients required cardiac surgery for extraction. Complications included sternotomy for subclavian vein injury (1), chest tube for caval perforation (1), innominate vein thrombosis (1), and partial clavicle removal for subclavian vein repair (2). There were no procedure-related deaths. CONCLUSIONS: Laser-assisted lead extraction is safe, but it is best performed in the operating room; it should be available for long-term leads, except when they are grossly infected, producing sepsis. Laser techniques have essentially eliminated the need for open surgical removal of retained leads.

Adult↗
PubMed2002

Influence of retrograde cerebral perfusion during aortic arch procedures.

BACKGROUND: Recent reports suggest dramatic improvement in outcome using retrograde cerebral perfusion (RCP) during operations on the arch; however, most investigators have compared contemporary results with historic controls. The purpose of this study was to determine the impact of RCP within the same patient population and time period. METHODS: From 1996 to 2000, 72 consecutive patients underwent an aortic arch procedure using hypothermic circulatory arrest (HCA) (31 acute dissection or rupture, 41 chronic dissection or aneurysm). Supplemental RCP was used in 36 patients, whereas 36 patients had HCA alone. The groups were similar in age, emergent status, and cardiopulmonary bypass time (p > 0.08), but HCA time was higher with RCP (40 +/- 15 minutes versus 29 +/- 14 minutes; p < 0.001). RESULTS: Operative mortality was 10% +/- 4% (+/- 70% confidence limit), and adverse outcomes (death or cerebrovascular accident) occurred in 14% +/- 4%, but there was no difference between HCA alone (8% +/- 5%, 14% +/- 6%) and HCA with RCP (11% +/- 5%, 14% +/- 6%) (p > 0.73). The incidence of transient neurologic dysfunction was also similar (HCA alone, 11% +/- 5%; HCA with RCP, 17% +/- 6%; p > 0.73). Multivariate risk factors for mortality included emergency operation and HCA time (p < 0.02). Risk factors for adverse outcome included emergency operation and atheromatous ascending aorta (p < 0.03). Risk factors for transient neurologic dysfunction included preexisting cerebrovascular disease and rewarming retrograde (femoral) rather than antegrade (through the graft) (p < 0.03). CONCLUSIONS: Supplemental RCP during HCA did not decrease mortality or neurologic complications. Retrograde rewarming through the femoral artery after completion of the distal anastomosis increased transient neurologic dysfunction. Therefore, RCP remains optional, but reperfusion should be antegrade to improve neurologic recovery.

Adult↗