Reduction of leg wound infections following coronary artery bypass surgery.

OBJECTIVE: To reduce the rate of infection at the saphenous vein harvest site after coronary artery bypass surgery, to identify predictors of infection and to determine the best method for leg wound closure. DESIGN: A randomized clinical trial was undertaken to determine the best technique for reducing the postoperative leg wound infection rate. Patients were allocated to one of four leg wound closure methods: staples, close immediately; staples, close after protamine administration; subcuticular sutures, close immediately; and subcuticular sutures, close after protamine. Risk factors evaluated were age, sex, diabetes, obesity, peripheral vascular disease, reoperation, time in surgery, wound length, wound depth, time that the wound was open, wound quality and harvest site. SETTING: The Walter C Mackenzie Health Sciences Centre, University of Alberta, Edmonton, Alberta. PATIENTS: All consenting patients undergoing elective coronary artery bypass surgery involving saphenous vein harvesting were considered for the study. Exclusion criteria were insertion of a drain, insertion of an intra-aortic balloon pump in the index limb and inability to complete follow-up at the authors' centre. Eighty patients were initially enrolled, with 77 completing the study. INTERVENTIONS: Patients underwent standard saphenous vein harvesting followed by wound closure as indicated by the study group. MAIN RESULTS: The major infection rate was reduced from 13% to 3% (P = 0.02). Each closure method was equally effective, and wound depth was the only factor related to infection. CONCLUSIONS: Leg wound infections continue to be a major source of morbidity after coronary bypass surgery.

Myocardial infarction complicated by ventricular septal rupture in a patient with polycythemia vera and minimal coronary ectasia.

Although it is known that patients with polycythemia vera (PV) are at increased risk of myocardial infarction (MI) secondary to thrombosis, ventricular septal rupture in this setting has never been reported. Ventricular septal rupture complicating a small anteroseptal MI is reported in a patient with PV and with only minimal ectasia of the left anterior descending coronary artery. Despite small infarct size these patients may be predisposed to myocardial hemorrhage, increasing the likelihood of myocardial rupture.

Spatiotemporal evolution of ventricular fibrillation.

Sudden cardiac death is the leading cause of death in the industrialized world, with the majority of such tragedies being due to ventricular fibrillation. Ventricular fibrillation is a frenzied and irregular disturbance of the heart rhythm that quickly renders the heart incapable of sustaining life. Rotors, electrophysiological structures that emit rotating spiral waves, occur in several systems that all share with the heart the functional properties of excitability and refractoriness. These re-entrant waves, seen in numerical solutions of simplified models of cardiac tissue, may occur during ventricular tachycardias. It has been difficult to detect such forms of re-entry in fibrillating mammalian ventricles. Here we show that, in isolated perfused dog hearts, high spatial and temporal resolution mapping of optical transmembrane potentials can easily detect transiently erupting rotors during the early phase of ventricular fibrillation. This activity is characterized by a relatively high spatiotemporal cross-correlation. During this early fibrillatory interval, frequent wavefront collisions and wavebreak generation are also dominant features. Interestingly, this spatiotemporal pattern undergoes an evolution to a less highly spatially correlated mechanism that lacks the epicardial manifestations of rotors despite continued myocardial perfusion.

Order in disorder: effect of barium on ventricular fibrillation.

BACKGROUND: Drugs that prolong cardiac refractoriness can decrease defibrillation energy requirements. In particular, barium, a relatively selective blocker of cardiac Ik1 channels, produces marked decreases in defibrillation energy. The mechanism of this effect is unknown, and may relate to modulation of the effect of defibrillatory shocks, or an alteration of the pattern of ventricular fibrillation (VF) by the drug. METHODS AND RESULTS: Accordingly, the effect of barium chloride was examined, 1.1 mg/kg followed by 0.1 mg/kg/min intravenously, or saline control, on the pattern of unipolar electrograms using a 120 electrode array, during 73 episodes of VF (37 after saline, 36 after barium ). For each episode of VF, peak-dV/dt associated with local activations and mean activation-activation (ACT-ACT) intervals for the last 2 s of a 10 s episode of VF were measured for each electrode. 'Organization' in VF was measured by the variability in ACT-ACT intervals, their visually assessed pattern, and the relation between local activations on adjacent electrodes. Voltage gradients were measured at each of 40 epicardial sites for each defibrillation shock, delivered at voltages ranging from to 20% to 100% successful in defibrillation. At identical voltage shocks (400 V), mean voltage gradients before and after barium were similar: 18+/-9 and 19+/-1.2 V/cm, respectively. Mean peak -dV/dt for all activations was -8.7+/-0.5 V/s before and -7.7+/-2.8 V/s after barium, suggesting no apparent change in local conduction velocity. When the lowest voltage gradient at any site was less than 3.5 V/cm, defibrillation was successful 14% of the time (two of 14 ) during control, but 88% of the time (14 to 16) after barium infusion (P<0.01). Mean ACT-ACT intervals after barium for all episodes over all electrodes was 107.5+/-14.1 ms, significantly longer than 89.7 +/-3.9 ms after saline, indicating a 20% increase in the cycle length of fibrillation. During saline control, local epicardial electrogram patterns showed irregular, variable morphology electrograms and a mean lowest SD of ACT-ACT intervals over any electrode of 5.1+/-1.5 ms, compared with 1.2+/-0.7 ms after barium (P < 0.0001). Following barium, most unipolar epicardial electrograms showed regular, phasic activations that appear to reflect an organized, uniformly repetitive local activation pattern, suggesting spatially homogeneous and temporally regular activation wavefronts. CONCLUSIONS: During VF after barium, despite an apparently disorganized surface electrocardiographic pattern, epicardial electrogram patterns are altered and reflect a more ¿ordered', homogeneous and regular local activation. This increased order may be in part responsible for the decreased defibrillation energy requirements observed after barium.

Aprotinin in children undergoing repair of congenital heart defects.

BACKGROUND: Aprotinin use in adults is increasing, and its use in children has recently been reported. METHODS: The efficacy of aprotinin in children was tested in 80 children. Patients were in four groups: reoperations (59), neonates (8), extremely cyanotic children (6), and other complex repairs (7). The results were compared with those of 55 control infants and children: reoperations (25), neonates (10), cyanotic (10) and complex (10). Treatment groups were identical in age, sex ratio, cross-clamp time, and bypass time. RESULTS: Patients treated with aprotinin had a significant reduction in chest tube drainage (16.5 +/- 9.8 versus 33.4 +/- 22.1 mL.kg-1.h-1; p < 0.001) and time to skin closure (64.2 +/- 23.7 versus 80.1 +/- 24.6 minutes; p < 0.001). Transfusion requirements were decreased in aprotinin-treated patients 4.2 +/- 3.4 versus 6.7 +/- 5.2 donors; p < 0.001). All of the control patients were exposed to at least one donor, whereas 10/80 (12.5%) of the aprotinin-treated group had no blood use (p < 0.006). There were no cases of renal insufficiency or allergic reactions in children receiving aprotinin. Three patients had thrombotic episodes: 2 superior vena caval problems and a lower extremity deep venous thrombosis. There were 3 cases of mediastinitis in the aprotinin group versus none in control patients (p < 0.05). CONCLUSIONS: We conclude aprotinin is an effective means of reducing bleeding, operating time, and donor exposure in infants and children. An increased rate of thrombosis and possibly mediastinitis are potential problems.

Epicardial cardiac source-field behavior.

The accurate determination of the spatial distribution of cardiac electrophysiological state is essential for the mechanistic assessment of cardiac arrhythmias in both clinical and experimental cardiac electrophysiological laboratories. This paper describes three fundamental cardiac source-field relationships: 1) activation fields, 2) electrotonic fields, and 3) volume conductor fields. The three cases are described analytically and illustrated with experimentally obtained canine cardiac recordings that capitalize on a recently formulated technique for in vivo cardiac transmembrane current estimation.

Significance of inwardly directed transmembrane current in determination of local myocardial electrical activation during ventricular fibrillation.

Ventricular fibrillation (VF) is the principle cardiac rhythm disorder responsible for sudden cardiac death in humans. The accurate determination of local cardiac activation during VF is essential for its mechanistic elucidation. This has been hampered by the rapidly changing and markedly heterogeneous electrophysiological nature of VF. These difficulties are manifested when attempting to differentiate true propagating electrical activity from electrotonic signals and when identifying local activation from complex and possibly fractionated electrograms. The purpose of this investigation was to test the hypothesis that the presence of a balanced inwardly and outwardly directed transmembrane charge, obtained from the ratio of the inward to outward area under the cardiac transmembrane current curve (-/+ Im area), could reliably differentiate propagating from electrotonic deflections during VF. To test this hypothesis, we applied a recently described technique for the in vivo estimation of the transmembrane current (Im) during cardiac activation. A 17-element orthogonal epicardial electrode array was combined with an immediately adjacent optical fiber array to record electrical and optically coupled transmembrane potential signals during VF. Recordings were obtained during electrically induced VF in six dogs to determine the Im associated with activation and the time course of repolarization, as well as unipolar electrograms and bipolar electrograms recorded at multiple center-to-center interelectrode distances from 0.2 to 3 mm. Propagating local activations were associated with the presence of an easily identified inwardly directed Im, with a balanced inward and outward charge (-/+ Im area approximately 1.0). Electrotonic wave-forms lacked this inward Im (-/+ Im area approximately 0.0). Normal Na(+)-mediated inward currents were directly demonstrated to be responsible for some activations during VF.

Aneurysm of the membranous ventricular septum producing subpulmonic outflow tract obstruction.

The authors report the case of a 31-year-old asymptomatic male who, following investigations for cardiac murmur, was found to have congenitally corrected (status solitus of the atria, left looping of the ventricles, leftward aorta in relation to the pulmonary artery [S,L,L]) transposition of the great vessels with significant right-sided ventricular outflow tract obstruction due to a large aneurysm of the membranous ventricular septum. Diagnosis was made with transesophageal echocardiography and confirmed during corrective surgery. The authors review the literature with regard to aneurysms of the membranous ventricular septum and their association with congenital heart disease, and they discuss the use of noninvasive tests aiding the diagnosis.

Barium decreases defibrillation energy requirements.

Certain antiarrhythmic drugs that inhibit myocardial repolarizing currents decrease defibrillation energy, but the effect of blocking particular currents on defibrillation is not well understood. We therefore investigated the effect of barium, a relatively selective blocker of inwardly rectifying potassium current (Ik1) on voltage and energy requirements for defibrillation in an open-chest dog model. Defibrillation energy and voltage requirements were assessed by delivering monophasic shocks through epicardial electrode patches at varying voltages to construct a dose-dependent curve of energy and voltage versus success in defibrillation. The energy and voltage for 50% success in defibrillation (E50 and V50, respectively) were determined by logistic regression. Monophasic action potential duration at 90% repolarization (MAPD90) was measured with a contact electrode, and ventricular refractory period (VERP) was measured. After baseline measurements were obtained of E50, V50, MAPD90, and VERP, saline (control) (n = 6) or barium (1.1 mg/kg/min for 5 min followed by 0.25 mg/kg/min) (n = 11) was administered. Defibrillation voltage and energy requirements and electrophysiologic measures were repeated after 30 and 120 min of barium or saline infusion. In control animals, there was no significant change with time in V50 (2.0 +/- 12.4 and -0.2 +/- 16.0% at 30 and 120 min, respectively), VERP (+3 +/- 5 and -2 +/- 3% at 30 and 120 min, respectively) or MAPD90 (+1 +/- 4 and -2 +/- 6, at 30 and 120 min, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal spinal cord syndrome associated with hypoplastic aortic arch and anemia.

Spinal cord syndrome is a rare postoperative complication in neonates. We describe a case occurring after surgical treatment of a hypoplastic aortic arch in the presence of anemia.

In vivo estimation of cardiac transmembrane current.

The ionic currents that cross the myocardial membrane during cardiac activation have a corresponding return path in the extracellular space. The transmembrane current (Im) during activation of cardiac cells in situ has previously been envisioned only in mathematical models. We have developed a remarkably simple in vivo technique that incorporates an electrode array with cellular dimensions to continuously estimate the extracellular counterparts of cardiac Ims. Mathematical modeling was performed for uniform plane wave propagation to clarify the biophysical basis and underlying assumptions inherent in this approach. Five-element electrode arrays incorporating 75-microns-diameter silver electrodes with center-to-center distances of 210 microns were experimentally verified to provide spatially sufficient samples for voltage gradient determinations of myocardial activation. Similar results were obtained with 25-microns-diameter electrodes at a center-to-center spacing of 65 microns. An estimate of Im was obtained from the derivative of the magnitude of the voltage gradient of the measured interstitial potentials. The inward component of Im generated by normal Na+ channel activation at 37 degrees C was measured in vivo to be less than 1 msec in duration, consistent with previously known voltage-clamp and simulation results. Intravenous KCl bolus injection was used to demonstrate the voltage-dependent depression of Na(+)-mediated Im in vivo, culminating in either severely depressed Na(+)-mediated or Ca(2+)-mediated activations. Normal Na(+)-, depressed Na(+)-, and possibly Ca(2+)-mediated currents can be recorded in vivo using this technique.

Right pulmonary artery obstruction after pulmonary artery banding.

Serial assessment of pulmonary artery flow by Doppler echocardiography was carried out in 15 infants after pulmonary artery banding. Three infants were identified as having branch pulmonary artery obstruction based on diastolic pulmonary artery flow. It is concluded that this flow profile may be specific for branch pulmonary artery obstruction after pulmonary artery banding.

An improved technique for his bundle recording and ablation in dogs.

Many physiological investigations of cardiac function require accurate control of heart rate. To examine heart rate effects at values lower than the intrinsic heart rate requires the ability to prevent an accelerated junctional rhythm from becoming dominant even after the sinus node is eliminated. A new method for the simple and reliable production of complete atrioventricular heart block in open-chest dogs is presented. It consists of two bonded parallel 22-gauge needles, one containing a bipolar recording electrode for localization at its tip and the other used for immediately adjacent formalin injection. The catheter is easily constructed, sterilizable, reusable, and durable, and can also provide a stable means of recording the His bundle electrical activity. Initial experiments performed in the first five dogs using this technique produced complete heart block with a stable ventricular escape rhythm in all five cases.

Mechanism of cardiac defibrillation in open-chest dogs with unipolar DC-coupled simultaneous activation and shock potential recordings.

The automatic implantable cardioverter-defibrillator has been shown to dramatically improve survival. The future refinement of these devices requires a clear understanding of their mechanism of action. We performed the following study to test two hypotheses: 1) When defibrillation is successful, fibrillating activity must be annihilated in a critical mass of both ventricles; and 2) when defibrillation is unsuccessful, at least one area of the ventricular mass has been left fibrillating. Unipolar Ag/AgCl sintered electrodes were directly coupled from triangular arrays at 40 epicardial locations (total, 120 recording sites) that covered both right and left ventricular surfaces and were designed to measure the voltage gradient generated by the shock at each triangular array as well as the underlying myocardial electrical activity before and immediately after the shock. An algorithm was developed and tested that reliably scored whether a postshock activation was a continuation of the immediately previous fibrillating activity. This technique was applied to 203 defibrillation attempts in six open-chest dogs during electrically induced ventricular fibrillation. There were 139 successful defibrillation attempts and 64 unsuccessful attempts. Monophasic truncated exponential 10-msec defibrillation shocks (0.5-35 J) were delivered through an anodal patch on the right atrium and a cathodal patch on the left ventricular apex. In all cases of unsuccessful defibrillation, at least one ventricular site could be clearly identified that failed to be defibrillated. In cases of successful defibrillation two distinct patterns were observed: 1) complete annihilation of fibrillating activity at all sites or 2) nearly complete cessation of fibrillating activity with a single area of persistent fibrillation that subsequently self-extinguished within one to three activations. This single site in the second form of successful defibrillation was located in the region of minimum voltage gradient produced by the defibrillating waveform and was occasionally accompanied by dynamic encapsulation with refractory tissue as a result of a wavefront emanating from a region that had undergone successful defibrillation. These results support the hypothesis that a critical mass of myocardium must be affected for successful defibrillation and that unsuccessful defibrillation is always accompanied by residual fibrillating activity in at least one site. The results also demonstrate that the size of the critical mass required for successful defibrillation can be less than 100%.

Anomalies of the left atrioventricular valve and related ventricular septal morphology in atrioventricular septal defects.

A characteristic feature of atrioventricular septal defects is a deficiency of the inlet part of the ventricular septum that results in a "scooped out" appearance. The depth of the scoop in relation to the disposition of the atrioventricular valves has been debated. To clarify the relation between the morphology of the ventricular septum and the disposition of the atrioventricular valves, we quantified these anatomic features in 151 hearts at autopsy to determine whether those features identified particular groups within the overall lesion. We found that 137 hearts had left atrioventricular valves with three leaflets. The left valve in the other 14 hearts exhibited a dual orifice, a two-leaflet or one-leaflet arrangement, or was imperforate. These anomalies could be analyzed in terms of a sequence of diminishing formation of the commissures. Also, three-leaflet valves displayed a variability in which the angular size of the mural leaflet correlated negatively with that of the inferior leaflet. In some of the hearts with a common atrioventricular orifice, the bridging leaflets did not meet over the ventricular septum, thus creating a "gap." The mural leaflet's angular size corresponded to a deficiency of the combined inferior-mural leaflet complex. Hearts with an abnormal disposition of the left atrioventricular valve had the ventricular septum "scooped" to a greater extent than those with a common orifice, although most had separate right and left atrioventricular orifices.

Epicardial activation times after defibrillation in open-chest dogs using unipolar DC-coupled activation recordings.

The widespread clinical application of implantable electrical defibrillation devices has engendered considerable interest into the mechanism of action of such devices. In addition, better means of rapid detection of postshock efficacy have been sought. The authors performed this study to test the following hypotheses: (1) postshock epicardial activation times may be used to differentiate successful from unsuccessful defibrillation attempts; and (2) successful defibrillation can be characterized by whether two or more activation wavefronts are simultaneously present on the epicardium after a defibrillation attempt. Unipolar Ag/AgCl sintered electrodes were directly coupled from 120 recording sites that covered both right and left ventricular surfaces. This technique was applied to 203 defibrillation attempts in 6 open-chest dogs during electrically induced ventricular fibrillation. There were 139 successful and 64 unsuccessful defibrillation attempts. The difference between the first and second post-shock activation times was significantly different between the successful and unsuccessful attempts. This difference was secondary to the activation time delay of the second post-shock activation cycle relative to the first post-shock activation cycle. When the first-to-second post-shock time delay was greater than 140 ms, the defibrillation attempt was found to be uniformly successful. In no case of successful defibrillation accompanied by total termination of ventricular fibrillation were more than two wavefronts simultaneously present on the heart after shock. In contrast, successful defibrillation accompanied by transient residual fibrillating activity or unsuccessful defibrillation attempts were observed to present with either two simultaneous activation wavefronts or an activation wavefront in temporal isolation.(ABSTRACT TRUNCATED AT 250 WORDS)

Subaortic stenosis in childhood: frequency of associated anomalies and surgical options.

In a 4-year period from July 1984 to July 1988, 21 children required surgical treatment for subaortic stenosis. Age at operation ranged from 12 months to 17 years (mean, 7.3 +/- 4.8 years). Associated anomalies were common and occurred in 13 patients (62%), including aortic valve insufficiency (eight), and stenosis (two), mitral valve stenosis (two) and insufficiency (one), and pulmonary valve stenosis (two) and absent pulmonary valve syndrome (one). A ventricular septal defect was present in five patients, and coarctation and patent ductus arteriosus occurred in three patients each. One patient had a complete atrioventricular septal defect, and one had an aortopulmonary window. Six patients had 15 previous procedures. The left ventricular to aortic gradient ranged from 20 to 170 mm Hg (mean, 59 +/- 43 mm Hg). The operation consisted of a transaortic resection (17), transventricular septal defect resection (two), a modified Konno procedure or septoplasty with preservation of the aortic valve (one), and a combined aortoventriculoplasty with homograft reconstruction of the ascending aorta and coronary reimplantation (one). There were no early deaths. One patient required pacemaker insertion for heart block. Follow-up ranged from 1 to 48 months (mean, 26.4 +/- 11.6 months). There was one late death 2 years after operation in the child with the aortopulmonary window who had Heath Edwards Type IV changes on a lung biopsy specimen at the original operation. One patient required reoperation for a residual gradient of 34 mm Hg 1 year after resection. Three patients still have aortic insufficiency. No cases of iatrogenic aortic valve injury occurred. Patients with subaortic stenosis represent a heterogeneous group. Early resection and additional procedures can be performed with a low mortality rate and can eliminate aortic insufficiency in many cases.