John W. Standeven

Pulmonary valve replacement: a comparison of three biological valves.

BACKGROUND We retrospectively reviewed the performance of the mosaic porcine, bovine pericardial, and homograft prostheses for pulmonary valve replacement to correct chronic pulmonary insufficiency. METHODS From January 1995 to August 2006, 82 patients (mean age, 22.7 years) underwent valve replacement with porcine (49 patients), bovine pericardial (18 patients), or pulmonary homograft (15 patients) prosthesis at a mean of 15.3 years after initial outflow tract reconstruction. Excluded were patients with extracardiac conduits, monocusp valves, or the Ross procedure. The groups were similar with respect to age, body surface area, degree of regurgitation, right ventricular dimension, right ventricular to pulmonary artery gradient, and valve size. Follow-up was longer in the homograft cohort (porcine, 20 +/- 27 months; pericardial, 42 +/- 21; homograft, 49 +/- 40; p < 0.01). RESULTS All three prostheses significantly reduce chronic pulmonary regurgitation, but late insufficiency was higher with homografts. Right ventricular dimension was significantly reduced in the stented but not the allograft cohorts. Late valve dysfunction was highest with homografts (54%), followed by porcine (19%) and pericardial valves (5.5%; p < 0.05. Functional class and mild to moderate tricuspid insufficiency significantly improved with pulmonary valve replacement. Early and late mortality was 3.6% and 1.2%, respectively. CONCLUSIONS All three prostheses performed similarly for 3 years. Pulmonary regurgitation developed more frequently in homografts albeit at a longer duration of follow-up.

Correlation of end-tidal CO2 to cerebral perfusion during CPR.

STUDY OBJECTIVE A number of studies have demonstrated a correlation between end-tidal carbon dioxide (ETCO2), cardiac output, and return of spontaneous circulation in experimental animals and in patients undergoing closed-chest CPR. Our study attempted to correlate ETCO2 to cerebral blood flow during cardiac arrest. DESIGN Sixteen piglets were anesthetized, intubated, and instrumented for cerebral blood flow studies. An ultrasonic flow probe was placed on both internal carotid arteries for continuous flow measurements. The animal was fibrillated, and closed-chest CPR was begun. Continuous ETCO2 measurements were obtained and compared with simultaneous internal carotid, cardiac output, and cerebral blood flow measurements. MEASUREMENTS AND MAIN RESULTS Correlations between ETCO2 and carotid and cerebral blood flow were determined using Pearsons method. The correlation between ETCO2 and total internal carotid flow was .58 (P = .01, Bonferronis adjusted P = .30). Correlation between ETCO2 and cerebral blood flow was .64 (P = .01, Bonferronis adjusted P = .09). A partial correlation coefficient for ETCO2 versus cardiac output was .70, whereas it was only .30 for ETCO2 versus cerebral blood flow. CONCLUSION Partial correlation coefficients suggest that ETCO2 correlates with cerebral blood flow when changes in cerebral blood flow parallel changes in cardiac output.

Cold Blood as the Vehicle for Potassium Cardioplegia

Cold blood with potassium, 34 mEq/L, was compared with cold blood and with a cardioplegic solution. Three groups of 6 dogs had 2 hours of aortic cross-clamp while on total bypass at 28 degrees C with the left ventricle vented. An initial 5-minute coronary perfusion was followed by 2 minutes of perfusion every 15 minutes for the cardioplegic solution (8 degrees C) and every 30 minutes for 3 minutes with cold blood or cold blood with potassium (8 degrees C). Hearts receiving cold blood or cold blood with potassium had topical cardiac hypothermia with crushed ice. Peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of the contractile element, pressure volume curves, coronary flow, coronary flow distribution, and myocardial uptake of oxygen, lactate, and pyruvate were measured prior to ischemia and 30 minutes after restoration of coronary flow. Myocardial creatine phosphate (CP), adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were determined at the end of ischemia and after recovery. Changes in coronary flow, coronary flow distribution, and myocardial uptake of oxygen and pyruvate were not significant. Peak systolic pressure and lactate uptake declined significantly for hearts perfused with cold blood but not those with cold blood with potassium. ATP and ADP were lowest in hearts perfused with cardioplegic solution, and CP and ATP did not return to control in any group. Heart water increased with the use of cold blood and cardioplegic solution. Myocardial protection with cold blood with potassium and topical hypothermia has some advantages over cold blood and cardioplegic solution.

Do Wrist Guards Protect Against Fractures

STUDY OBJECTIVE To determine whether wrist guards increase the fracture threshold for wrist and forearm fractures. METHODS We conducted a controlled, blinded experimental study using matched cadaveric arms-one fitted with a wrist guard-dropped with the use of a device designed to simulate a fall. We measured the mean number of drops before the occurrence of fracture, mean height and velocity change to fracture, mean kinetic energy, mean peak acceleration (in Gs), and summed impulse [weight (kilograms) x delta velocity (meters/second)] to fracture with and without wrist guards. Fracture severity was compared with the use of an ordinal ranking system and analyzed with the Mann-Whitney rank-sum test. RESULTS Wrist guards were associated with a statistically significant increase in the number of drops, mean drop height, mean kinetic energy, and summed impulse required to cause a fracture. Fractures also tended to be less severe when wrist guards were used. CONCLUSION The biomechanical evidence of a protective effect of wrist guards against wrist fractures seen in this study, coupled with previous epidemiologic evidence, is strong enough to warrant pediatricians, family practitioners, and emergency physicians to counsel skaters to use these devices when using roller skates, skateboards, or in-line skates.

The inflatable penile prosthesis: failure of the rear tip extender in reducing the incidence of cylinder leakage.

Of 184 patients who have received an inflatable penile prosthesis at our institution since 1974, 43 per cent have undergone reoperation, the majority of which were owing to cylinder leakage. Comparison by life-table analysis of cylinders placed before and after introduction of the rear tip extender does not show an improvement in cylinder survival to date.

Cold Blood–Diltiazem Cardioplegia

The calcium channel blocker, diltiazem, has been studied in the same model used for evaluation of cold blood-potassium cardioplegia. Six dogs (Group 1) had one hour of myocardial ischemia with topical ice (myocardial temperature, 7 degrees +/- 2 degrees C) after coronary perfusion with 200 ml of cold blood (5 degrees +/- 1 degree C) containing diltiazem, 400 micrograms per kilogram of body weight. Seven dogs (Group 2) had two hours of ischemia after perfusion with 200 ml of cold blood containing 200 micrograms/kg and reperfusion every 30 minutes with 100 ml of cold blood and diltiazem, 100 micrograms/kg. Baseline studies were repeated after rewarming and 40 minutes of reperfusion. No inotropic agents or calcium were used. Heart rate, peak systolic pressure, velocity of the contractile element, peak + rate of rise of left ventricular pressure (dP/dt), peak - dP/dt, dP/dt over common peak isovolumic pressure, left ventricular compliance and stiffness, and heart water were unchanged in Group 1. In Group 2, heart rate slowed (p less than 0.025) and compliance decreased (p less than 0.02). In both groups, coronary vascular resistance declined (p less than 0.001) and recovery of adenosine triphosphate (p less than 0.001), adenosine diphosphate (p less than 0.025), and the adenosine pool (p less than 0.001) was impaired. Ultrastructure was well preserved, but myofibrillar lesions were noted in Group 2. Diltiazem cardioplegia was associated with good functional recovery, but there was impairment of high-energy phosphate metabolism.

Left coronary ostial stenosis: Comparison with left main coronary artery stenosis

We compared 147 consecutive patients who had left coronary ostial stenosis with 254 consecutive patients who had left main coronary artery stenosis treated with coronary artery bypass grafting. Mean age for the left main group was 61.6 years versus 59.7 years for the left ostial group (p = not significant [NS]). In the left ostial group, 43.5% were female and in the left main group, 12% (p less than 0.005). Prior myocardial infarction had occurred in 53% of patients with left main stenosis and 36% of patients with left ostial stenosis (p less than 0.005). There were 2.45 +/- 1.00 diseased vessels in the left main group and 1.96 +/- 1.09 in the left ostial group (p less than 0.0005). Seven (3%) of the patients with left main stenosis had no associated coronary disease (greater than 50%) versus 24 (16%) of the left ostial group (p less than 0.005). The degree of left main stenosis was 90% or more in 28.3% of patients versus 42.8% with equivalent ostial narrowing (p less than 0.01). Left ventricular function was better in the left ostial group than in the left main group (1.61 +/- 0.93 versus 2.02 +/- 1.11, respectively; p less than 0.0005). One-month mortality was 10 patients (3.9%) in the left main group and 8 (5.4%) in the left ostial group (p = NS). Perioperative infarction occurred in 8.6% of patients with left main stenosis and 4.7% of patients with left ostial stenosis (p = NS). Mean follow-up was 6.1 years for the left main group and 5.4 years for the left ostial group.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Venous Arterialization: Acute Hemodynamic, Metabolic, and Chronic Anatomical Observations

Nine dogs that had anastomosis of the internal mammary artery (IMA) to the left anterior descending coronary vein (LADV) were studied acutely on right-heart bypass. Occlusion of the left anterior descending coronary artery (LADA) and LADV without venous arterialization resulted in a significant decline in stroke work, total coronary flow, and myocardial oxygen uptake; with reactive hyperemia an increase in lactate and pyruvate consumption resulted. Occlusion of the LADA and LADV with VA did not change these variables greatly, except for a marked increase in total coronary flow with reactive hyperemia. Chronic venous arterialization in 14 dogs was associated with a 14% mortality, while 10 controls had a 40% mortality. Dogs were killed at six weeks, and prior angiography in 9 showed patency of the IMA to the heart without filling of cardiac veins. All dogs had infarcts in the distribution of the LADA; these infarcts were smaller in dogs with venous arterialization. The anastomoses were obliterated by mature or maturing fibrous tissue, with alteration of the vein so that it was frequently not discernible, while the IMA was well preserved. Distal veins had foci of intimal proliferation, subintimal fibrosis, and medial hypertrophy. Although venous arterialzaiton provides protection for the acutely ischemic myocardium, this effect does not persist, perhaps because of anastomotic occlusion due to fibrous proliferation.

A Servocontrolled Atrial-Aortic Assist Device: Experimental Findings and Clinical Experience

A servocontrol system was developed to regulate a single roller pump left atrial-aortic (La-A) assist device. Responsiveness of the servomechanism to blood volume changes, myocardial damage, and mitral regurgitation was evaluated in 5 sheep and 6 dogs. Myocardial damage was induced by occlusion of coronary arteries. and the hemodynamic effects of La-A assistance were evaluated. While La-A assistance reduced left atrial pressures to low levels, the left ventricular end-diastolic pressure remained elevated in the severely damaged heart. LaA-assistance was used in 3 patients. Two were weaned from cardiopulmonary bypass after failure of intraaortic balloon counterpulsation, and 1 is a long-term survivor. The third was supported for 48 hours after attempt repair of complex congenital heart disease. The servocontrol device added to the safety of prolonged La-A assistance. This mode of assistance should be considered when intraaortic balloon counterpulsation has failed.

Topical Cardiac Hypothermia: The Effect of Methylprednisolone Sodium Succinate

We evaluated the effects of methylprednisolone sodium succinate (MPSS) on 60 minutes of myocardial ischemia during profound (5 degrees C) topical cardiac hypothermia (ice chips) in a canine right heart bypass preparation. The ventricular function curve shifted to the right and downward, but not significantly, after ischemia, and stroke work declined significantly for both control and treated dogs. Contractility (rate of rise of left ventricular pressure and maximum velocity of the contractile element) declined for both groups but not significantly. Total coronary flow, oxygen consumption, and metabolism of lactate and pyruvate were not different for control and treated dogs. Ultrastructure of the outer and inner myocardium did not demonstrate benefit from MPSS. Intracellular and extracellular edema of moderate severity was slightly worse in the subendocardium, and reversible mitochondrial injury of a mild to moderate degreee was symmetrically present. Ice-related injury was not noted. We were unable to deomonstrate that pretreatment with MPSS favorably alters cardiodynamics or ultrastructure after 60 minutes of profound topical cardiac hypothermia.