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Biomedical subjects

Lawrence H Cohn

Publications and source records attributed to Lawrence H Cohn.

71 records · Page 4Linked to original sources
PubMed2003

Biological vs. mechanical aortic root replacement.

OBJECTIVES: Although age and co-existing coronary disease are major determining factors when deciding valve choice (mechanical vs. biological) in simple aortic valve replacement, no studies have documented selection criterion for biological (BIO) vs. mechanical (MECH) aortic root prosthesis. METHODS: Two hundred and twenty-one consecutive patients underwent elective aortic root replacement with either BIO (homograft, n=111, Freestyle, n=25) or MECH composite grafts (n=85). Median age in BIO was 53 years and in MECH 54 years (P=NS). Groups were similar in gender, NYHA class and ejection fraction (BIO, EF=59% vs. MECH, EF=55%), but the need for concomitant coronary artery bypass grafting (CABG) did differ between groups (MECH=35% vs. BIO=17%, P=0.003). Mean follow-up was 42+/-28 months for mortality and 39+/-28 months for morbidity. RESULTS: Full root replacement was performed in 213 patients (96%) and hemi-root in eight (4%). The most common underlying etiologies were annulo-aortic ectasia (n=82, 37%), calcified-degenerative (n=73, 33%) and bicuspid/congenital aortic valve disease (n=39, 18%). Operative mortality was 1.5% for BIO and 2.4% for MECH (P=0.5). By univariate analysis there was a trend towards greater 5-year survival in BIO (92.4% vs. 88.2%, P=0.068). By multivariate analysis, increasing age (HR=2.4, P=0.003), previous valve replacement (HR=4.7, P=0.024), concomitant CABG (HR=3.7, P=0.032), and perioperative stroke (HR=9.9, P=0.0005) were all independent predictors of late death. The 5-year freedom from valve-related complications was similar in both groups (BIO=93% vs. MECH=86%, P=0.5). CONCLUSIONS: Elective aortic root replacement is an exceedingly safe operation. At mean follow-up of 4 years, there is no meaningful difference in early or mid term valve-related results between BIO and MECH aortic root replacement. Continued evaluation for late valve-related complications in this cohort will be necessary to determine the advantages, if any, of one prosthesis over the other.

Adult↗
PubMed2003

Transcriptional profiling and growth kinetics of endothelium reveals differences between cells derived from porcine aorta versus aortic valve.

OBJECTIVE: Valvular tissue and aorta calcify at different rates when placed as fresh homografts or cryopreserved allografts. Furthermore, differences between valvular endothelial cells and aortic endothelial cells are not well appreciated. We established primary cultures of valve and aortic endothelial cells derived from swine and tested transcriptional and proliferative differences on various extracellular matrices. METHODS: Transcriptional profiling was performed on primary cultures of porcine valve and aortic endothelial cells. We extracted total RNA from both cell types and created cDNA libraries. We scored for 847 genes important in signal transduction pathways, and measured their expression on valve and aortic endothelial cells. To determine if there were functional differences between aortic and valvular cells, their growth rate was determined by cell counting on various extracellular matrices. RESULTS: Of 847 genes investigated, 69 (8.1%) were transcriptionally active on aortic endothelial cells and 89 (10.5%) on valve endothelial cells. Common to both cell types were 55 genes, which represents 79.7% (55/69) of activated genes on aortic endothelial cells and 61.8% (55/89) of those in valve endothelial cells. Remarkable features of the analysis included Ephrin ligand and receptor specificity for cell type, a potential fibroblast growth factor autocrine loop in both cell types, as well as upregulation of the platelet-derived growth factor receptor in valvular cells. Aortic endothelial cells were noteworthy of upregulation of vascular endothelial cell growth factor-B and vascular cell adhesion molecule. Proliferation analysis revealed that valve endothelial cells grew more rapidly (12-fold over control) than aortic endothelial cells (3-fold over control). Furthermore, valve endothelial cells proliferated most rapidly on gelatin or collagen, whereas aortic endothelial cells were most proliferative on lysine or laminin. CONCLUSIONS: Valve and aortic endothelial cells have different transcriptional and proliferative profiles. The knowledge of these differences may be an exploitable strategy in the future rational design of artificially engineered valve surfaces and in the study of the valve antigenicity, immunogenicity and structural failure.

Animals↗
PubMed2003

Improvement of intraoperative antibiotic prophylaxis in prolonged cardiac surgery by automated alerts in the operating room.

OBJECTIVE: To assess the impact of an automated intraoperative alert to redose prophylactic antibiotics in prolonged cardiac operations. DESIGN: Randomized, controlled, evaluator-blinded trial. SETTING: University-affiliated hospital. PATIENTS: Patients undergoing cardiac surgery that lasted more than 4 hours after the preoperative administration of cefazolin, unless they were receiving therapeutic antibiotics at the time of surgery. INTERVENTION: Randomization to an audible and visual reminder on the operating room computer console at 225 minutes after the administration of preoperative antibiotics (reminder group, n = 137) or control (n = 136). After another 30 minutes, the circulating nurse was required to indicate whether a follow-up dose of antibiotics had been administered. RESULTS: Intraoperative redosing was significantly more frequent in the reminder group (93 of 137; 68%) than in the control group (55 of 136; 40%) (adjusted odds ratio, 3.31; 95% confidence interval, 1.97 to 5.56; P < .0001). The impact of the reminder was even greater when compared with the 6 months preceding the study period (129 of 480; 27%; P < .001), suggesting some spillover effect on the control group. Redosing was formally declined for 19 of the 44 patients in the reminder group without redosing. The rate of surgical-site infection in the reminder group (5 of 137; 4%) was similar to that in the control group (8 of 136; 6%; P = .42), but significantly lower than that in the pre-study period (48 of 480; 10%; P = .02). CONCLUSION: The use of an automatic reminder system in the operating room improved compliance with guidelines on perioperative antibiotic prophylaxis.

Antibiotic Prophylaxis↗
PubMed2003

The evolution of mitral valve surgery: 1902-2002.

The evolution of the surgical therapy of mitral valve disease emanates from original statements by British cardiologists in 1902 and anecdotal individual surgical cases in 1923 and 1925. Considerable amounts of experimental investigation during these years and after World War II in 1948 finally resulted in the widespread use of closed mitral commissurotomy, a successful therapy for noncalcified mitral stenosis. The history of mitral valve surgery then rapidly progressed with a variety of prosthetic and bioprosthetic valve devices, ultimately, to a considerable number of successful valve repair operations with prosthetic ring annuloplasty. The authors conclude with a discussion of the current status of minimally invasive mitral valve surgery, both by direct vision and robotic assistance. The entire evolution of thought and technique of mitral valve surgery is summarized in this paper from 1902-2002.

Adult↗
PubMed2002

Aortic valve surgery after previous coronary artery bypass grafting with functioning internal mammary artery grafts.

BACKGROUND: Aortic valve surgery after coronary artery bypass grafting (CABG) in the setting of patent pedicled internal mammary artery (IMA) grafts poses a high risk because of the underlying ischemic and valve disease. Unlike mitral valve surgery or CABG, in which aortic clamping (AoX) may be optional, aortic valve surgery uniformly requires AoX unless circulatory arrest is used. Management of the IMA graft in these circumstances has traditionally involved dissection and clamping to prevent regional myocardial warming and cardioplegia "washout" during AoX. An alternative strategy involves avoiding dissection of the IMA, leaving the IMA graft open and establishing moderate-to-deep hypothermia during AoX and cardioplegic arrest. To date, no study has been published documenting the safety and efficacy of the latter practice. METHODS: A total of 94 patients who had patent IMA graft and underwent aortic valve surgery under AoX and cardioplegia between April 1992 and March 2001 were analyzed. The IMA was avoided and left open during AoX, and the patients were cooled systemically (median 20 degrees C). Patients ranged in age from 55 to 90 years (median 73.5 years). Ejection fraction was 15% to 83% (median 50%). Of the patients, 18 (19%) underwent minimally invasive upper hemi-resternotomy. Analysis for predictors of outcome was performed. RESULTS: The operative mortality, perioperative myocardial infarction (MI), and stroke rates were 6.4%, 7%, and 11%, respectively. No significant independent predictors of operative mortality or MI could be identified in the multivariate analysis, although a trend was shown for operative mortality with urgent procedures and patients requiring concomitant surgery of the ascending or arch aorta or aortic root. Advanced age and prolonged cardiopulmonary bypass predicted stroke in the multivariate analysis. There were five (5%) IMA injuries, all occurring during reentry or mediastinal dissection, but none in the subgroup of patients who underwent minimally invasive procedures. All patients survived. CONCLUSIONS: Patients undergoing aortic valve surgery after CABG in the presence of patent IMA represent a potentially high-risk group. Because AoX is almost uniformly required, a decision regarding the management of the IMA pedicle is needed. We have found that leaving the IMA undissected and unclamped is a reasonable strategy, provided that systemic cooling for myocardial protection is established to prevent regional warming and to compensate for cardioplegia washout effect during AoX.

Aged↗
PubMed2002

Risk factors and management of endocarditis after mitral valve repair.

BACKGROUND AND AIMS OF THE STUDY: The authors' nine-year experience with patients requiring mitral valve reoperations for endocarditis after previous mitral valve repair is reported. METHODS: Between June 1991 and June 2000, 1,275 mitral valve repairs were performed at the authors' institution. During this time, nine patients with prior mitral valve repair presented with mitral valve (non-recurrent) endocarditis requiring surgical correction. Etiology at the initial mitral valve repair was ischemic in four patients (44%), floppy valve in one patient (11%), Libman-Sacks endocarditis in one (11%), irradiation-induced degeneration in one (11%), and endocarditis in two cases (22%). Median patient age was 61 years (range: 36-81 years). Median ejection fraction was 50% (range: 23-70%), and seven patients (78%) presented urgently or emergently. The median time interval between the two procedures was 8.6 months (range: 28 days to 14.3 years). RESULTS: Certain risk factors were identified in these patients, including systemic infections, prosthetic implants in the bloodstream, and subsequent invasive procedures. The mitral valve was re-repaired in one patient (11%), while eight patients (89%) required valve replacement. All required excision of the ring. Hospital mortality was 11% (n = 1). Postoperative complications included perioperative myocardial infarction in two cases (25%), low cardiac output in two (25%), and prolonged ventilatory support in four (50%). There was no perioperative stroke, and no late recurrence of endocarditis. CONCLUSION: The study findings suggest that the incidence of (non-recurrent) endocarditis after mitral valve repair requiring surgical intervention is infrequent. Attempts at re-repair may be successful only in selected patients. Reoperation was accomplished with acceptable morbidity and mortality, and often required mitral valve replacement; however, late results indicated the absence of prosthetic valve endocarditis.

Adult↗
PubMed2002

Cardiac positioning using an apical suction device maintains beating heart hemodynamics.

BACKGROUND: Cardiac positioning during off-pump coronary artery bypass (OPCAB) using deep pericardial sutures (DPS) typically results in some degree of hemodynamic compromise. We sought to determine whether cardiac positioning using an apical suction device was hemodynamically superior to DPS. METHODS: Five healthy pigs underwent sternotomy and instrumentation to measure right atrial (RA) pressure, left ventricular (LV) pressure and volume, and aortic pressure and flow. These variables were recorded at baseline, with simple attachment of the apical suction device (Xpose Access Device, Guidant, Inc.), and during exposure of the posterior descending artery (PDA) and obtuse marginal (OM) branches of the left circumflex artery using DPS and the apical suction device. RESULTS: Application of the apical suction device to the beating heart in neutral anatomic position did not result in any statistically significant change in hemodynamics compared to baseline except for a small decrease in RA pressure. DPS positioning resulted in statistically significant compromise in nearly all measured hemodynamic parameters, including cardiac output (-21% PDA, -30% OM), mean arterial pressure (-18% PDA, -26% OM), and stroke work (-31% PDA, -38% OM). In addition, LV end-diastolic pressure decreased (-59% PDA, -51% OM) while RA pressure increased (+17% PDA, +16% OM). Similar target exposure using the apical suction device resulted in near-baseline hemodynamics. The only statistically significant changes were a modest decrease in cardiac output (-18% OM) and RA pressure (-11% PDA). CONCLUSION: DPS positioning significantly compromises hemodynamics due to reduced LV filling. The apical suction device provides good exposure with less hemodynamic compromise.

Animals↗
PubMedDate not supplied

Minimally invasive valve surgery: what the pathologist should know.

Minimally invasive approaches in cardiac surgery have emerged as an alternative to standard techniques particularly in patients undergoing valvular surgery. Their established benefits for the patients are likely to cause their widespread use in the future. The purpose of this is to provide an overview of modern minimally invasive approaches in valvular surgery with an emphasis on aspects of the surgery relevant for cardiovascular pathologists.

Heart Valve Diseases↗
PubMedDate not supplied

Management of mild aortic stenosis during coronary artery bypass surgery: an update, 1992-2001.

BACKGROUND: "Prophylactic" aortic valve replacement (AVR) in patients with asymptomatic, mild-to-moderate aortic stenosis (AS) at the time of CABG is controversial. In 1994, we reported our initial experience involving 44 patients and have now updated our series in an attempt to further evaluate outcomes. METHODS: Between January 1992 and July 2001, 100 consecutive patients underwent reoperative AVR following previous CABG. Forty patients had their initial surgery at the Brigham & Women's Hospital (BWH) and 60 patients had their coronary surgery elsewhere. None of the 40 BWH patients had a mean valve gradient greater than 25 mmHg at the time of CABG. RESULTS: The mean time interval from CABG to AVR for the entire group was 9.0 years (range: 1.4-21 years). Overall operative mortality (OM) was 7% including 5 deaths (10.2%) among 49 patients requiring additional CABG at the time of AVR and 2 deaths (3.9%) among 51 patients without additional coronary artery intervention. This OM rate was a notable decrease from our earlier report of 18.2% (P = 0.07). Furthermore, operative mortality decreased progressively from 15.4% in 1992-1993 to 0% in 2000-2001 (P = NS). CONCLUSION: The OM of reoperative AVR following CABG has fallen in recent years. Given the relevance of newer techniques and approaches, it may be reasonable to adopt an expectant management approach in patients with asymptomatic mild-to-moderate AS (i.e., mean systolic gradient less than 25 mmHg) at the time of CABG.

Aged↗
PubMedDate not supplied

Right ventricular volume measurement using the conductance catheter method: validation in excised porcine hearts.

The conductance catheter method for measuring right ventricular (RV) volume changes was assessed in seven excised porcine hearts. A 5-FG conductance catheter was placed within a latex balloon and positioned in the RV cavity of seven freshly excised porcine hearts. Conductance was recorded while saline was withdrawn from the intraventricular balloon in 2 ml decrements. Linear regression analysis of measured conductance versus reference volumes was computed. The effect of left ventricular (LV) filling and catheter length on conductance derived RV volume was also determined. Conductance derived volumes were highly correlated with reference volumes [R2 0.976, standard deviation (SD) 0.035]. The mean gradient of regression was 0.97 (SD 0.10), and it was not significantly affected by LV volume alterations. However, when we analyzed LV filling, a small but significant increase in the y-intercept was observed (LV empty 3.11 ml, SD 1.71; LV full 4.58, SD 2.39; p = 0.008). Introduction of the catheter through either the tricuspid or pulmonary orifices were both effective in ventricular volume measurement. The effect of mismatch between the catheter length and the RV long axis dimension was evaluated by changing the position of the active sensing electrodes along the catheter body. Conductance measurements, obtained from catheters shorter than the long axis of the RV, still maintained a highly linear correlation with real volume, but regression gradients were significantly reduced (long 0.975, SD 0.087; medium 0.787, SD 0.094; small 0.589, SD 0.091; p < 0.001). These results show that a conductance catheter of appropriate length can accurately measure RV volume, despite the complex shape and geometric changes associated with ventricular filling.

Animals↗
PubMedDate not supplied

The surgical treatment of heart failure. A new frontier: nontransplant surgical alternatives in heart failure.

Heart failure may affect 500,000 new people each year. Heart transplantation has leveled off at approximately 2,500-3,000 cases per year in the United States. Thus, new nontransplant surgical alternatives may be necessary to treat many of the patients who progress to intractable Class III, or especially Class IV heart failure. In addition to left ventricular assist devices, other operations have been used and are now being developed for this purpose. These include left ventricular resection (Batista operation), mitral valve repair, autologous skeletal muscle cardiac assist, splint and compression devices, as well as left ventricular reconstruction by the Dor procedure. All of these procedures have been, and are currently being, evaluated for the surgical treatment of congestive heart failure and they will be reviewed in this article. Although many appear very promising, ongoing trials and retrospective reviews will be increasingly necessary to vigorously define which of the nontransplant surgical alternatives are the best procedures going forward for the large numbers of patients with congestive failure.

Animals↗
PubMedDate not supplied

Evolution of redo cardiac surgery: review of personal experience.

This presentation summarizes the author's personal observations on the major advances in reoperative cardiac surgery. They include earlier referral for cardiac prosthetic and bioprosthetic cardiac valve dysfunction, alternative incisional approaches to minimize injury to adherent cardiac structures, alternative perfusion sites, improved hemostasis on cardiopulmonary bypass, improved myocardial protection, tailoring the valve prosthesis to the patients' anatomy and clinical situation, "no-touch" technique in reoperative coronary artery surgery, and increasing use of hypothermic circulatory arrest for recurrent ascending arch and descending thoracic pathology. Each of these is explained in detail with the appropriate references and retrospective data collections where appropriate. This risk of reoperative cardiac surgery will continue to improve as these and additional techniques continue to evolve and become simplified. Further investigation into the clinical uses of minimally invasive techniques including robot technology, may eventually reduce morbidity and mortality of reoperations to that equal to primary operations.

Aortic Valve↗
PubMedDate not supplied

Minimally invasive mitral valve repair with and without robotic technology in the elderly.

An increasing number of elderly persons require mitral valve surgery, primarily for mitral regurgitation. Minimally invasive mitral valve repair, including robotic surgery, has been shown to be feasible and safe in the general population. Minimally invasive cardiac surgery is especially beneficial in the elderly because it decreases trauma and speeds recovery. The authors conducted a retrospective review of 123 cases of minimally invasive mitral valve repair in elderly patients aged 70 years and older and five robotic mitral valve repairs using the da Vinci surgical system (Intuitive Surgical, Inc., Sunnyvale, CA) in one octogenarian. The authors review their 9 years of experience with minimally invasive mitral valve repair in the elderly and compare and contrast other forms of surgery in the elderly, including robotic mitral valve repair.

Aged↗
PubMedDate not supplied

Determinants of outcomes for postcardiotomy VAD placement: an 11-year, two-institution study.

OBJECTIVE: Ventricular assist device (VAD) placement after postcardiotomy failure is associated with a high mortality. We sought to determine prognostic factors in order to help better select patients who may benefit from VAD placement. METHODS: From January 1992 to January 2003, 63 patients out of approximately 30,000 cardiac surgery patients (0.21%) developed postcardiotomy failure requiring VADs. Planned VAD for bridge to transplant or bridge to recovery were excluded. Multivariate logistic regression analysis, based on pre-VAD placement parameters, was used to determine prognostic factors for in-hospital 30-day mortality. RESULTS: Overall operative mortality was 73% (46 of 63). Multivariate logistic regression analysis identified median age </=50 (each additional year) (OR = 0.85, 95% CI = 0.77 to 0.95, p = 0.004) and median base deficit >/=0 mEq/L (each additional mEq/L) prior to VAD placement (OR = 0.60, 95% CI = 0.48 to 0.91, p = 0.012) to be independent predictors of improved 30-day survival. CONCLUSIONS: Postcardiotomy failure is a rare event but is associated with a very poor prognosis despite salvage therapies utilizing VADs. Age </=50 years and base deficit >/=0 (mEq/L) prior to VAD placement are associated with improved 30-day survival.

Adolescent↗