Prospective evaluation and clinical utility of on-site monitoring of coagulation in patients undergoing cardiac operation.

Although laboratory coagulation tests permit a rational approach to both diagnosis and management of coagulation disorders after cardiopulmonary bypass, their clinical utility is limited by delays in obtaining results. This study was designed to evaluate prospectively the impact of on-site coagulation testing on blood product use, operative time, and intraoperative management of microvascular bleeding. Patients who underwent cardiac procedures involving cardiopulmonary bypass and subsequently developed microvascular bleeding were randomly assigned to receive either standard therapy (n = 36) or therapy defined by a treatment algorithm based on results from an on-site coagulation monitoring laboratory (n = 30). No differences were found between treatment groups in hematologic assay data, operative procedures, or duration of cardiopulmonary bypass. Patients treated in accordance with on-site laboratory results (algorithm therapy) received significantly less intraoperative fresh frozen plasma (0.4 +/- 1.1 U versus 2.4 +/- 2.8 U; p = 0.0006) during the treatment interval, had shorter operative times, and had less mediastinal chest tube drainage during the initial perioperative interval (158 +/- 169 ml versus 326 +/- 258 ml; p = 0.003) than did patients in the standard therapy group. Patients who underwent algorithm therapy also received fewer platelet (1.6 +/- 5.9 versus 6.4 +/- 8.2 U; p = 0.02) and red blood cell (1.9 +/- 1.7 U versus 4.1 +/- 4.1 U; p = 0.01) transfusions after the operation. Nine of 36 (25%) standard group patients received initial therapy which differed from that which would have been guided by the on-site algorithm protocol. Our findings indicate that rapid and accurate coagulation test results can guide specific therapy and optimize treatment of microvascular bleeding in patients who undergo cardiac operations.

The impact of heparin concentration and activated clotting time monitoring on blood conservation. A prospective, randomized evaluation in patients undergoing cardiac operation.

A whole blood hemostasis system (Hepcon) provides both activated clotting time and accurate whole blood heparin concentration measurements via an automated protamine titration method. This study was designed to prospectively evaluate the impact of heparin and protamine administration using this system on the incidence and treatment of bleeding after cardiopulmonary bypass. Two hundred fifty-four patients requiring cardiopulmonary bypass were enrolled in this prospective study over a 7-month period. Patients treated with antifibrinolytic agents (aprotinin, epsilon-aminocaproic or tranexamic acid) were excluded. Patients were randomly assigned to either a control (n = 127) or intervention (n = 127) group. For control patients, the anticoagulation protocol consisted of an initial fixed dose of 250 U/kg of heparin, and additional 5000 U heparin doses were administered if the activated clotting time was less than 480 seconds. Heparin was neutralized with an initial fixed dose of protamine (0.8 mg protamine per milligram total heparin). For the intervention group, an initial dose of heparin was based on an automated heparin dose-response assay. Additional heparin doses were administered if the heparin concentration was less than the reference concentration or for an activated clotting time less than 480 seconds. The protamine dose was based on the residual heparin concentration. Treatment of excessive bleeding after cardiopulmonary bypass was based on an algorithm using point-of-care testing with whole blood prothrombin time, activated partial thromboplastin time, heparinase activated clotting time, and platelet count. No differences between the two treatment groups were identified in reference to demographic factors, preoperative anticoagulant medications, preoperative coagulation data, number of reoperations, or combined procedures and duration of cardiopulmonary bypass. Indirect evidence for coagulation factor consumption was demonstrated in control patients by more prolonged whole blood prothrombin time and activated partial thromboplastin time values after cardiopulmonary bypass when compared with values obtained in the intervention group. Patients in the intervention cohort received greater doses of heparin (intervention: 612 +/- 147, control: 462 +/- 114 U/kg, p < 0.0001) and had lower protamine to heparin ratios (intervention: 0.70 +/- 0.64, control: 0.94 +/- 0.21, p = 0.0001) compared with control patients. Patients in the intervention cohort received significantly fewer platelet (intervention: 1.7 +/- 3.6 U, control: 3.7 +/- 6.7 U, p = 0.003), plasma (intervention: 0.4 +/- 1.3 U, control: 1.4 +/- 2.5 U, p = 0.0001), and cryoprecipitate units (intervention: 0.0 +/- 0.0 U, control: 0.2 +/- 1.2 U, p = 0.04) during the perioperative interval than control patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Five-year experience with the maze procedure for atrial fibrillation.

Between September 25, 1987, and December 31, 1992, 75 patients (53 men, 22 women; average age, 52 years) underwent the maze procedure for the treatment of atrial fibrillation. Six patients had undergone a previous cardiac operation and 28% underwent concomitant cardiac procedures in addition to the maze procedure. One patient (1.3%) died 10 days after undergoing a combined maze procedure and Morrow procedure for the management of chronic atrial fibrillation and hypertrophic obstructive cardiomyopathy. Postoperative atrial pacemakers were required in 40%: 26% for preoperative sick sinus syndrome and 6% for iatrogenic injury of the sinus node, and 8% had pacemakers in place preoperatively. As of December 31, 1992, 65 patients had been followed up for at least 3 months after operation (range, 3 to 63 months). The maze procedure cured atrial fibrillation, restored atrioventricular synchrony, and preserved atrial transport function in 64 of 65 patients (98%). The procedure has been curative without the need for medications in 58 of 65 patients (89%) and with the need for medications in 6 of 65 (9%), with medications failing in only 1 of the 65 patients (2%). The results support the maze procedure as the treatment of choice in patients with medically refractory symptomatic atrial fibrillation.

From fisherman to fibrillation: an unbroken line of progress.

The modern era of cardiac arrhythmia surgery was initiated by Dr Will C. Sealy in May 1968, when he performed the first successful surgical division of an accessory pathway for the treatment of the Wolff-Parkinson-White syndrome. During the subsequent 25 years, arrhythmia operations evolved through a series of innovative surgical procedures capable of curing essentially all refractory clinical arrhythmias. The lessons learned during the development of these surgical procedures ultimately led to the refinement and eventual success of less invasive catheter techniques that have now replaced most of these surgical techniques. The surgical experience gained during these years also made possible the current surgical procedure that is used to treat the most complex, and the most common, of all cardiac arrhythmias, atrial fibrillation. Few areas of any specialty are as clearly defined as the unbroken line of progress that extends from Dr Sealy's first procedure in 1968 to the successful surgical treatment of atrial fibrillation in 1994.

Echocardiographic automatic boundary detection to measure left atrial function after the maze procedure.

Automatic boundary detection (ABD) is a new echocardiographic modality providing continuous on-line measurements of cavitary area throughout the cardiac cycle. The maze procedure is a new surgical intervention designed to restore sinus rhythm and mechanical atrial contraction as a definitive treatment for patients with atrial fibrillations for whom medical therapy has failed. To evaluate whether ABD may define left atrial function in patients after the maze procedure, we obtained pulsed Doppler recordings of mitral inflow velocity and echocardiographic ABD in 25 patients, 6 +/- 2 months after the maze procedure. We measured the left atrial end-systolic cavitary area, mid-diastolic area before atrial contraction, and end-diastolic area (in square centimeters). Left atrial contraction by Doppler was compared with that derived by ABD in patients who underwent the maze procedure and control subjects (n = 13), both qualitatively and quantitatively (atrial filling fraction vs active atrial contraction [ABD] where atrial contraction (in percent) = (mid-diastolic area - end-diastolic area) x 100/(end-systolic area - end-diastolic area in percent]). Restoration of atrial contraction after the maze procedure was detected by Doppler in 19 patients (76%) and by ABD in 21 patients (84%). The atrial filling fraction was 19 +/- 4% in patients compared with values of 34% +/- 8% in control subjects (p < 0.001). By ABD atrial contraction was 20% +/- 6% in patients whereas control subjects exhibited values of 41% +/- 14% p < 0.001). The Doppler-derived atrial filling fraction and ABD-derived atrial contraction were closely correlated (r = 0.91; p < 0.001; y = 0.59x + 8.6). Thus Doppler techniques complemented by ABD provide direct quantitative indexes of left atrial function throughout the cardiac cycle. Although left atrial contraction and filling are reduced after the maze procedure, left atrial function is restored in most patients with a history of atrial fibrillation, and echocardiographic ABD is a sensitive technique for its detection.

Operations for atrial fibrillation.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and May 1, 1991, this procedure was applied in 22 patients with either paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications and each patient failed an average of 5.2 drugs preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been cured of atrial fibrillation with surgery alone. One late isolated episode of atrial flutter occurred in a patient who is now receiving encainide. Preservation of atrial transport function has been documented in all of the patients postoperatively and all have experienced marked clinical improvement.

Wolff-Parkinson-White syndrome: discharge planning.

Some patients with Wolff-Parkinson-White (WPW) syndrome have potentially life-threatening arrhythmias. Symptomatic WPW is associated with tachycardias that are supraventricular in origin. Discharge teaching after surgical correction of WPW is critical to restoring the patient's previous life-style.

Restoration of atrial function after the maze procedure for patients with atrial fibrillation. Assessment by Doppler echocardiography.

BACKGROUND: The purpose of the present study was to evaluate the effects of the maze procedure on atrial function in patients operated on for atrial fibrillation. The maze procedure is a new surgical intervention that is designed to restore sinus rhythm and active mechanical atrial contraction as a definitive treatment for patients with atrial fibrillation. METHODS AND RESULTS: Doppler echocardiographic analysis of mitral and tricuspid inflow as well as pulmonary venous flow velocity was carried out in 46 patients 8 +/- 7 months after the maze procedure, and results were compared with those obtained from 27 age-matched control subjects. To evaluate atrial contraction, we determined the presence of atrial contribution to ventricular filling at the mitral and tricuspid valve levels and measured the percent atrial filling fractions of the left and right atria. To evaluate atrial compliance, we measured the systolic and the systolic-to-diastolic flow velocity ratios of the pulmonary venous inflow. Results were compared with similar measurements obtained from control subjects. Restoration of active atrial contraction was detected in 40 of the 46 patients (87%); right atrial contraction was noted in 38 patients (83%), and left atrial contraction was noted in 28 patients (61%). In patients with active atrial contraction, the percent atrial filling fraction of the right atrium was comparable to that of control subjects (32 +/- 7% versus 33 +/- 8%, P = NS), whereas that of the left atrium was smaller (20 +/- 5% versus 36 +/- 7%, P < .005). In addition, compared with control subjects, pulmonary venous flow in maze patients exhibited a reduced systolic component (17 +/- 4 versus 53 +/- 16 cm/s, P < .001) and decreased systolic-to-diastolic flow velocity ratio (0.3 +/- 0.01 versus 1.1 +/- 0.3, P < .001) and velocity integral ratio (0.3 +/- 0.01 versus 1.3 +/- 0.4, P < .001), all suggesting decreased left atrial filling. CONCLUSIONS: The maze procedure restores active right atrial contraction and improves left atrial contraction in most patients. Obtained measurements suggest decreased left atrial compliance and reduced left atrial contribution to ventricular filling compared with control subjects. Despite the reduced indexes, qualitative restoration of function in either atria should translate in improved atrioventricular synchrony and reduction in thromboembolic events in patients with chronic or paroxysmal atrial fibrillation.

Regional and global myocardial circulatory and metabolic effects of isoflurane and halothane in patients with steal-prone coronary anatomy.

The use of isoflurane in patients with coronary artery disease remains controversial because of the possibility of "coronary steal". In this study, the effects of isoflurane and halothane on global and regional myocardial blood flow and metabolism were compared, and the relationship between steal-induced myocardial ischemia and the administered volatile anesthetic was investigated in 40 patients with steal-prone coronary anatomy undergoing elective coronary artery bypass operations. The patients were randomly assigned to receive either isoflurane or halothane (0.5 MAC inspired concentration) immediately after induction with fentanyl (50 micrograms/kg). Hemodynamic measurements and blood samples were obtained at preinduction, postintubation, preincision, poststernotomy, at 60 min after beginning isoflurane or halothane, and precannulation (a total of 238 study events). Throughout the study, heart rate was kept constant by atrial pacing at approximately postintubation values while arterial pressure was maintained within 10% of postintubation values with fluid administration or phenylephrine infusion. Overall, systemic hemodynamic changes observed during the study were similar in the two groups. Myocardial ischemic episodes were defined as a new electrocardiographic ST-segment shift of greater than or equal to 0.1 mV, new echocardiographic regional wall motion abnormalities (RWMA) and/or myocardial lactate production (MLP). A total of 18 new ischemic episodes were detected in 15 patients (7 episodes during isoflurane in 7 patients and 11 during halothane in 8 patients). Ten (56%) episodes were related to acute hemodynamic abnormalities, whereas 8 (44%) were random and unrelated to changes. Seven episodes were detected by echocardiography (38%), 6 by MLP (33%) and 1 by ECG (6%) only, whereas concomitant echocardiographic abnormalities and MLP were observed during 2 episodes (11%), echocardiographic and ECG during 1 (6%), and ECG and MLP during 1 other (6%). Ratios of regional to global coronary venous flow, coronary vascular resistance, myocardial oxygen content, and lactate extraction, along with hemodynamic data obtained during these episodes, do not support coronary steal for the development of myocardial ischemia. We conclude that in patients with steal-prone coronary anatomy anesthetized with fentanyl, neither isoflurane nor halothane administered at concentrations used in the current study is likely to cause myocardial ischemia by the coronary steal mechanism.

On-site prothrombin time, activated partial thromboplastin time, and platelet count. A comparison between whole blood and laboratory assays with coagulation factor analysis in patients presenting for cardiac surgery.

BACKGROUND: Although available hemostasis assays from institutional laboratories permit an analytical approach to diagnosis and treatment of coagulation disorders following cardiopulmonary bypass, their clinical utility has been limited by delays in obtaining results. The development of instrumentation for on-site testing allows rapid return of results. This study was designed to compare whole blood (WB) results obtained from on-site coagulation assays with values provided by our institutional laboratory (LAB). METHODS: After Institutional Human Studies Committee approval, 362 patients presenting for cardiac surgery requiring cardiopulmonary bypass were enrolled in this study. Prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count (PLT) assays were performed in both WB and LAB systems. PT, aPTT, and PLT measurements were compared between WB and LAB assays using blood specimens obtained from at least two time points for each patient. Normal range values for both PT and aPTT methods were determined by using measurements from a normal reference population. Coagulation factor levels were measured in a subset of patients to characterize the response of PT and aPTT assays to individual and multiple factor levels. To employ Bayes' theorem and calculate predictive indexes (e.g., sensitivity, specificity), the disease or factor deficiency was determined using factor levels. Predictive indexes were used to evaluate the ability of PT and aPTT assays to identify factor deficiency. RESULTS: PLT counts were similar between systems. Linear regression and bias analysis demonstrated similar results for WB and LAB PT and discordant results for aPTT measurements. Both PT assays had a similar normal range, whereas a wider distribution of results was evident for the WB aPTT normal range. Although statistically greater slopes for factor:aPTT regressions were observed for the WB system, WB aPTT correlated better with factor V and with factor V, VIII, and XII levels (multivariate linear regression). Diagnostic performance for factor levels less than 0.3 and 0.4 U/ml was similar for both WB and laboratory PT and aPTT assays. WB and LAB PT and aPTT assays performed similarly in detecting factor deficiency in the period after cardiopulmonary bypass. CONCLUSIONS: WB PT and PLT values correlate well with those obtained from the LAB. The discrepancy between measurement systems in aPTT values is probably a reflection of both different normal ranges and responsiveness to factor deficiency. These WB assays provide coagulation results that can accurately identify patients with quantitative deficiencies in platelets and coagulation factors.

Evaluation of complete blood count results from a new, on-site hemocytometer compared with a laboratory-based hemocytometer.

OBJECTIVE: To compare point-of-care results obtained from an on-site hemocytometer with values provided by an institutional laboratory instrument. DESIGN: A prospective laboratory evaluation. SETTING: The central laboratory and cardiac surgical intensive care unit of a university-affiliated tertiary care center. PATIENTS: Normal range comparison was performed using blood specimens routinely obtained from 48 hospitalized patients for complete blood count analysis. The second evaluation was performed on blood specimens routinely obtained (in the intensive care unit) after cardiac surgery involving extracorporeal circulation in a series of 187 consecutive patients. MEASUREMENTS AND MAIN RESULTS: Hemoglobin concentration, platelet count, mean corpuscular volume, mean platelet volume, and red and white blood cell counts were measured with both on-site (MD 16, Coulter Electronics, Hialeah, FL) and laboratory (STKS, Coulter Electronics) instruments. Hematocrit and red cell distribution width were calculated using measured variables. Blood specimens were obtained from two distinct patients series. To evaluate measurement values within the normal range, a series of 48 routinely obtained blood specimens for complete blood count analysis in our institutional laboratory were utilized for concurrent analysis with the on-site hemocytometer. To evaluate measurement values out of the normal range, a second comparison involved measurements performed on blood specimens obtained in the cardiac surgical intensive care unit for complete blood count analysis. Linear regression demonstrated good correlations between on-site and laboratory hemoglobin concentration (r2 = .97), hematocrit (r2 = .95), platelet count (r2 = .97), mean corpuscular volume (r2 = .91), red cell distribution width (r2 = .80), and red (r2 = .95) and white (r2 = .96) blood cell count results. A marginal correlation was observed between mean platelet volume values (r2 = .47). Bias analysis (mean +/- 2 SD) demonstrated similar measurements between on-site and laboratory hemoglobin concentration, hematocrit, platelet count, red blood cell count, white blood cell count, mean platelet volume, mean corpuscular volume, and red cell distribution width. CONCLUSIONS: On-site hemoglobin concentration, hematocrit, white blood cell count, red blood cell count, red cell distribution width, and platelet count values compare well with those results obtained from the laboratory. The MD 16 hemocytometer (Coulter Electronics) provides on-site hematologic results that can provide an accurate and rapid quantitative assessment of platelets, and red and white blood cells. Rapid access to information obtained from this type of system may be clinically useful, especially in critically ill patients.

Successful surgical treatment of atrial fibrillation. Review and clinical update.

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and July 1, 1991, this procedure was applied in 22 patients with paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications, and each patient failed to receive the desired therapeutic benefits of an average of five drugs administered preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been successfully treated for atrial fibrillation with surgery alone. Three patients developed one late isolated episode of atrial flutter at 5, 6, and 15 months postoperatively, and each of these patient's symptoms is now controlled by a single antiarrhythmic drug. Preservation of atrial transport function has been documented in all patients postoperatively, and all have experienced marked clinical improvement.

Electrophysiologic basis, surgical development, and clinical results of the maze procedure for atrial flutter and atrial fibrillation.

After more than a decade of experimental and clinical research into the basic mechanisms underlying atrial fibrillation, we were able to develop a surgical procedure that appears to cure the arrhythmia. This surgical procedure has been used in 100 patients in our institution and in a total of approximately 130 patients by surgeons in other institutions. The surgical results have been excellent, which indicates the sophisticated electrophysiologic mapping systems are unnecessary and that the results are not surgeon-specific.