Impact of biventricular and left ventricular pacing on hemodynamics and left ventricular dyssynchrony compared with right ventricular pacing in the early postoperative period following cardiac surgery

Objectives

The aims of this study were to test the hypotheses that in the postoperative period following corrective surgery for congenital heart defects: (i) atrio-right ventricular (RA-RV) pacing decreases cardiac output (CO) compared with right atrial (RA) pacing, (ii) atrio-biventricular (RA-BiV) and left ventricular (RA-LV) pacing improves CO compared with RA-RV pacing.

Study design

Prospective observational study.

Patients

Children 0-2 years of age referred for surgery of congenital heart defects were studied during intrinsic rhythm and atrial, atrio-right ventricular, atrio-left ventricular and atrio-biventricular pacing. CO, extrapolated from mean systolic aortic velocity (MSAV), and left ventricular dyssynchrony were assessed using transthoracic echocardiography.

Results

RA-RV pacing induced a significant decrease in CO (MSAV 0.52 ± 0.19 m/s to 0.46 ± 0.16 m/s, p = 0.01) and a significant increase in LV dyssynchrony (8.7 ± 7.9 ms to 33 ± 21 ms, p = 0.001). RA-BiV pacing induced a significant increase in CO (MSAV 0.46 ± 0.16 m/s to 0.52 ± 0.18 m/s, p = 0.01) and a significant decrease in LV dyssynchrony (33 ± 21 ms to 7 ± 4 ms, p = 0.0003) compared with RA-RV pacing. RA-LV pacing induced a significant decrease in LV dyssynchrony (33 ± 21 ms to 9 ± 7 ms, p = 0.0007) without a significant improvement of CO compared with RA-RV pacing.

Conclusions

RA-BiV pacing improves CO compared with RA-RV pacing in the early postoperative period following pediatric cardiac surgery. This improvement is related to a reduction in left ventricular dyssynchrony.     

The dynamic anterior mitral annulus

Background

The anterior mitral annulus is considered a fixed structure. Recent data suggest otherwise. This study tested the hypothesis that the size of the anterior annulus varies with hemodynamic loading and ventricular contractility.

Methods

Sonomicrometry array localization measured annular area, total annular circumference, anterior circumference, and posterior circumference in 6 sheep before and after neosynephrine increased systolic blood pressure by at least 150% during atrial pacing at 120 beats/min. In 6 additional animals the same dimensions were measured during atrial pacing (at 120 and 150 beats/min) and during isoproteronol infusions to increase heart rate to 120 and 150 beats/min.

Results

Neosynephrine increased systolic total annular circumference from 99.7 ± 5.5 mm to 106.9 ± 9.6 mm. Anterior circumference increased from 40.8 ± 4.0 mm to 45.3 ± 5.7 mm whereas posterior circumference only increased from 59.0 ± 5.5 mm to 61.6 ± 7.0 mm. Low isoproteronol infusion decreased systolic total annular circumference from 107.5 ± 8.3 mm to 101.9 ± 10.6 mm. Most of this change occurred in the posterior circumference. Higher infusions of isoproteronol decreased total annular circumference from 106.8 ± 8.3 mm to 98.3 ± 9.7 mm. At this higher inotropic state the decrease in annular size was similar in the anterior and posterior annulus.

Conclusions

In sheep, the anterior annulus is a dynamic structure that varies in size in response to changes in hemodynamic loading and ventricular contractility.     

Papaverine delivery to the internal mammary artery pedicle effectively treats spasm

Background

Left internal mammary artery spasm is well recognized during coronary artery bypass operations. Papaverine has been used by many surgeons to maximize mammary artery flow perioperatively, but the best delivery method is not known. We analyzed two techniques used at our institution.

Methods

Fifty-eight patients were randomized into three groups to compare papaverine's ability to prevent spasm and to treat established spasm. Group 1 was control and no treatment was employed. In group 2, papaverine was injected with a blunt needle through the endothoracic fascia parallel to the mammary artery before harvest to assess spasm prevention. In group 3, papaverine was delivered perivascular in an identical manner to group 2 but after the mammary artery was dissected from the chest wall. This group was an evaluation of spasm treatment. Drug dosage was the same for both groups and routine bypass grafting was performed. Before anastomosing the mammary artery to the left anterior descending artery, blood flow was recorded for 15 seconds and flow per minute calculated. Cardiopulmonary bypass pressures were maintained at 70 mm Hg during collection.

Results

Mean blood flows were: group 1 = 86.2 mL/min, group 2 = 122.5 mL/min, and group 3 = 139.7 mL/min. Left internal mammary artery flow in group 3 was statistically different from control (p = 0.0457). Group 2 flow approached but did not reach statistical significance (p = 0.0874). Mammary artery dissection times for the three groups were not different.

Conclusions

Papaverine delivery to the left internal mammary artery after dissection treats spasm effectively, improves blood flow at the time of its anastamosis to the left anterior descending artery, and avoids any risk of intimal injury. Injection of papaverine before mammary artery harvest does not shorten dissection time, and flow is not statistically improved.     

Comparison of longevity, pacing, and sensing characteristics of steroid-eluting epicardial versus conventional endocardial pacing leads in children

OBJECTIVE: Because of either cardiac anatomy or small size, pacing in children often occurs by means of epicardial leads. The disadvantage of epicardial leads is the shorter longevity of these leads compared with endocardial leads. During short-term follow-up, improved stimulation thresholds were found for the newer steroid-eluting epicardial leads. The longevity of these leads may be better than that of conventional epicardial leads. An improved longevity of epicardial leads may influence the choice to either epicardial or endocardial pacing in children. METHODS: We studied the longevity and the pacing and sensing characteristics of 33 steroid-eluting epicardial pacing leads (group I, 15 atrial, 18 ventricular) implanted between November 1991 and October 1996 in 20 children with a mean age of 7.6 +/- 6.5 years (mean +/- SD), and 29 endocardial pacing leads (group II, 15 atrial, 14 ventricular) implanted during the same period in 21 children with a mean age of 11.7 +/- 4.7 years. RESULTS: The mean follow-up in group I was 2.9 +/- 1.6 years and in group II 3.1 +/- 1.7 years (P =.61). The 2-year survival of the leads in group I was 91% +/- 5% and in group II 86% +/- 7% (P =.97). Lead failure occurred in both groups in 4 leads (P =.85). Chronic stimulation and sensing thresholds were similar. CONCLUSIONS: Steroid-eluting epicardial leads have the same longevity as the conventional endocardial leads. Pacing and sensing thresholds were similar and did not change during follow-up. Therefore steroid-eluting epicardial pacing leads are a good alternative for endocardial leads in small children and in children with congenital heart disease.     

VATS-guided epicardial pacemaker implantation

Background: In neonates and infants epicardial stimulation may be preferred to endocardial stimulation because of growth-associated lead problems and the risk of vascular complications associated with transvenous electrodes. This study analyzes the feasibility of atrioventricular implantation of a new epicardial lead using the video-assisted thoracic surgical (VATS) technique in an animal model. Methods: Bipolar steroid-eluting epicardial leads were implanted in seven young white pigs. In five animals bipolar atrial and ventricular pacing leads (n= 10) were inserted and fixed by the VATS technique, while two animals served as controls and underwent implantation through anterolateral thoracotomy. Surgical feasibility, pacing, and sensing thresholds of the leads as well as hemodynamic parameters during pacing were studied. Histological changes beneath the electrodes were evaluated 1 week after the implantation. Results: All animals survived the pacemaker lead implantation. One animal which underwent thoracotomy died because of irreversible ventricular fibrillation induced by rapid ventricular pacing. One animal in the VATS group exhibited intraoperative herniation of the heart through the pericardial window. All animals with left-sided VATS implantations demonstrated good individual pacing and sensing threshold values. The mean cardiac output was 1.6 times higher during AAI-mode pacing as compared to VVI-mode pacing at a heart rate of 140/min. One animal died postoperatively due to respiratory failure. No displacements of the pacemaker leads were observed in the survivors. Conclusion: While VATS-guided implantation of epicardial, atrial, and ventricular leads is feasible, technical improvements of the system are mandatory for safe clinical application. Received: 14 October 1996/Accepted: 14 April 1997     

Left heart atrial and ventricular epicardial pacing through a left lateral thoracotomy in children: a safe approach with excellent functional and cosmetic results.

OBJECTIVE: Left heart atrial and ventricular epicardial pacing through a left lateral thoracotomy is an alternative approach for lead insertion in children, avoiding venous access complications and right ventricular stimulation, without compromising sporting or musical activities. We analyzed the survival and performance of left atrial and left ventricular epicardial pacing leads, and present mid-term follow-up data. METHODS: Seventy-five bipolar steroid eluting pacing leads (Medtronic CapSure Epi 4968) were implanted in 41 children, aged 8.6+5.1 years. Pacing systems included 34 DDDR and 7 VVIR. Pacing leads were inserted through a muscle-sparing left lateral thoracotomy, and sutured to the left atrial appendage or atrium, and to the left ventricle. The generators were buried behind the abdominal muscles or between the thoracic muscle layers. Congenital heart disease with previous cardiac surgery was present in 25 children. Indications for pacing were post-operative heart block (n=14), sinus node disease (n=13), congenital heart block (n=9), and various (n=5). Threshold values and measured data were obtained at 6-month intervals. The mean follow-up was 3.8+2.9 years. RESULTS: There was no mortality or major morbidity, with excellent functional and cosmetic results. Lead survival was 94 and 86% for atrial leads, and 97 and 86% for ventricular leads, at 1 and 5 years, respectively. There were five reoperations for lead fracture (n=2), insulation break (n=1), oversensing (n=1), and infection (n=1). Device reprogramming was required in three instances. In the absence of acute lead failure, mid-term follow-up shows very satisfactory and stable lead performance. CONCLUSIONS: Left heart atrial and ventricular epicardial pacing leads inserted through a left lateral thoracotomy demonstrate a high probability of survival, with favorable pacing characteristics, and optimal sensing thresholds at mid-term follow-up. Epicardial left heart pacing is reliable, and easy access can be achieved through a cosmetic and functional muscle-sparing left lateral thoracotomy.     

Comparison of left and right atrial epicardial pacing in patients with congenital heart disease

Background. Complex congenital heart disease (CHD) often necessitates the use of epicardial pacing. Adequate right atrial (RA) sensing and pacing thresholds are often difficult to obtain due to suture line scarring and RA dilatation. The purpose of this study was to evaluate the placement of left atrial (LA) epicardial leads in children.

Methods. Patient demographics, pacing, and sensing data of atrial pacing systems implanted between January 1994 and January 1997 were collected.

Results. Forty-nine pacing systems were implanted: 14 LA epicardial, 19 RA epicardial, and 16 transvenous in the right atrium. Lead impedance, current, and energy were similar in the two epicardial groups throughout the study. Energy thresholds (ET) were lower in the LA than RA at 6 months, and 1 and 2 years (p < 0.05). Analysis of post-Fontan patients performed alone revealed a lower ET in the LA as compared with the RA. Pacing and sensing parameters from transvenous leads are presented for relative comparison.

Conclusions. Transvenous leads are most efficient but often contraindicated in complex CHD. LA leads offer lower energy thresholds than RA leads with similar sensing parameters.     

Improved reliability of post-operative ventricular pacing by use of bipolar temporary pacing leads.

The study compared the clinical reliability of using a bipolar epicardial wire (6495, Medtronic) over a unipolar type (FEP15, Ethicon) for post-operative pacing in coronary artery surgery. Atrial and ventricular wires of both types were implanted in 18 patients. Sensitivities and pacing thresholds were tested for 5 consecutive days. Results show that pacing thresholds were better maintained with the bipolar wire in both atria and ventricles. However, sensing failures were frequent in the atrial position (34% vs 9.3% compared with unipolar). By contrast, in the ventricle, no sensing failures occurred (0% vs 17.6% compared with unipolar). Furthermore, sensing magnitude was significantly better (11.13+/-1.32 vs 5.65+/-0.53 mV, P<0.001). We conclude that a single 6495 bipolar wire is effective for temporary ventricular pacing, whilst double unipolar wires remain a useful strategy for securing atrial sensing and pacing.     

A comparison of steroid-eluting epicardial versus transvenous pacing leads in children

OBJECTIVE: To evaluate the acute and chronic performance of steroid-eluting (SE) epicardial (EPI) pacing leads as compared to SE transvenous (TV) pacing leads in children. METHODS: From 1989 through 1997, 55 children with congenital heart disease received a total of 85 SE pacing leads, of which 38 were EPI and 47 TV. The mean age of children receiving EPI leads was younger than those receiving TV leads (7.7 months vs 15.1 years, p = 0.001), and they had shorter follow-up (17.2 months vs 36.2 months, p < 0.001). All leads were evaluated for acute and chronic sensing and capture thresholds, and impedance. RESULTS: Acute and in particular chronic atrial and ventricular sensing and capture thresholds in SE EPI and TV leads were essentially equivalent. [table: see text]. The chronic impedance of TV leads (atrial 525 ohms, ventricular 520 ohms) was consistently higher than EPI leads (atrial 404 ohms, ventricular 386 ohms). CONCLUSION: At intermediate follow-up, SE EPI leads are functionally equivalent to SE TV leads. We recommend the use of SE EPI leads as long as practically feasible prior to using the TV approach in children who will require a life-time of pacing.     

Permanent cardiac pacing after the Fontan procedure

Permanent cardiac pacing after a Fontan procedure is complicated by complex cardiovascular anatomy. Of 332 patients undergoing the Fontan procedure at the Mayo Clinic, we evaluated 15 who postoperatively required permanent pacing (mean age 16.5 years, range 4 to 31 years). Underlying congenital cardiac defects included univentricular heart in nine patients, double-outlet right ventricle in three, and tricuspid atresia in three. The indication for pacing was postoperative heart block in seven patients, congenital heart block in five, postoperative sick sinus syndrome in two, and heart block because of previous operation in one. Pacemakers were implanted immediately postoperatively in 11 patients and 12 to 57 months later in four patients. VVI systems were used in nine patients, DDD in four, AAI in one, and a Medtronic Activitrax VVI in one. All ventricular leads were epicardial. Four atrial leads were transvenous endocardial and one was epicardial. Three patients died 4, 9, and 69 months later of causes unrelated to pacing. Among the 12 survivors, mean follow-up was 34 months (range 1 to 107 months). Two patients had a total of three episodes of loss of ventricular capture because of increased chronic thresholds. Our current approach to pacing after a Fontan procedure includes (1) intraoperative placement of temporary atrial and ventricular electrodes, (2) intraoperative attachment of a permanent ventricular epicardial lead for congenital or surgically induced high-grade atrioventricular block, (3) postoperative insertion of transvenous atrial leads if dual-chamber pacing is indicated, and (4) use of programmable pulse generators with high output capability.     

Postoperative assessment of the univentricular repair by dynamic radionuclide studies

Background

The purpose of this investigation was to determine the role of radionuclide studies in evaluating postoperative Fontan hemodynamics and to quantify its diagnostic accuracy.

Methods

One hundred five patients (105), aged 11 months to 35 years old, who had undergone univentricular repair, underwent first-pass and multigated acquisition scan 1 month to 10 years after univentricular repair. Forty-five patients with evidence of Fontan failure underwent radionuclide studies using Technetium-99 m as well as cardiac catheterization (group 1). The remaining sixty randomly selected patients with excellent functional status received radionuclide studies alone (group 2). The receiver operating characteristic curve analysis was done to quantify the diagnostic accuracy of the first-pass study.

Results

There was paradoxical filling of the right lung after femoral injection in all cases of tunnel or conduit obstruction. A first-pass transit time of 16 to 25 seconds (mean ± standard deviation [SD] = 18.82 ± 2.69) was always associated with Fontan failure and high right atrial pressure (range = 20 to 24 mm Hg, mean ± SD = 22.02 ± 1.58). A first-pass transit time of 16 seconds was associated with a sensitivity of 100% and a specificity of 93.33%. The predictive accuracy of a positive or negative result was 91.8% and 100% respectively. The area measured under the receiver operating characteristic curve indicates that 99.41% (SE ± 0.0035) of the time, the value of first-pass time is higher for the Fontan failure group (group 1) compared to the normal group (group 2; p = 0.000).

Conclusions

Our data indicate that Fontan circuit can be reliably evaluated for both anatomic and functional flaws by radionuclide studies; radionuclide first-pass time may be used to predict the chances of Fontan failure postoperatively as well as its presence; and in the presence of atrial fibrillation with fast ventricular rate, analysis using first-pass radionuclide may be impossible and gated equilibrium radionuclide angiocardiography may be the preferred method. Inspection of the systemic ventricular time-activity curve is of crucial importance in this regard.     

Changes in right ventricular dimensions and performance after passive cardiac containment

Background

Previous studies have shown that the cardiac support device (CSD) improves left ventricular structure and function in patients with heart failure by preventing further cardiac enlargement. The aim of this study was to identify effects on the right ventricle (RV).

Methods

Ten male patients with idiopathic dilated cardiomyopathy underwent electron-beam computed tomographic (CT) examination within 1 month before, and 6 to 9 months after CSD implantation. The RV end-diastolic and end-systolic volumes (EDV, ESV) and diameters (EDD, ESD), stroke volume (SV), ejection fraction (EF), total and forward RV output (RVO, fRVO), and tricuspid regurgitation fraction (TRF) were calculated.

Results

The EDV measurements decreased from 182.1 ± 49.6 to 137.5 ± 37.0 mL, ESV from 114.8 ± 47.0 to 68.3 ± 23.8 mL, EDD from 48.2 ± 6.6 to 41.6 ± 7.1 mm, and ESD from 39.6 ± 6.9 to 32.7 ± 6.5 mm (p < 0.05 for each). Ejection fraction increased from 38.5 ± 8.9 to 52.0% ± 7.7% and fRVO from 4.0 ± 0.8 to 4.6 ± 1.1 L/min (each with p < 0.05). TRF decreased from 18.2 ± 14.1 to 10.4% ± 13.5%, whereas SV and RVO remained nearly unchanged. Postoperatively, RV volumes, EF, and fRVO were not different from 15 age- and gender-matched normal control patients.

Conclusions

Implantation of a CSD leads to a decrease in RV size and improved RV performance. These data together with the results of previous studies demonstrating improved left ventricular structure and function confirm the biventricular nature of recovery with the CSD.     

Evaluation of epicardial microwave ablation lesions: histology versus electrophysiology

Background

Pulmonary vein isolation is a hallmark in current surgical ablation for atrial fibrillation. However, validation of isolation remains cumbersome. We evaluated electrophysiologic and not histologic means to test isolation.

Methods

In 16 mongrel dogs, robot-assisted epicardial beating-heart microwave ablation (FLEX 10) was performed around the pulmonary veins. Electrophysiologic isolation was tested by pacing at 4 times threshold values inside and outside the pulmonary veins (exit and entrance block). The histology of lesions was studied for transmurality and continuity of the lesion lines. In 5 dogs, lesions were studied at various time intervals.

Results

Histologic evaluation of the lesions showed incomplete (48% ± 20%) circumferential myocardial damage in all dogs with acute lesions. Electrophysiologic evaluation showed completion of the box (entrance and exit block) in 8 dogs and in another 5 dogs after repeated ablation (p < 0.01 compared with histologic evaluation). Electrophysiologic evaluation of the dogs with chronic lesions showed completed lesions in 4 of 5 dogs directly after ablation. At follow-up (1 to 3 weeks), the isolations remained electrophysiologically complete. Histologic evaluation of the lesions 1 to 3 weeks after ablation showed complete (100%) circumferential lesions in all 4 dogs (p < 0.001 compared with the histology of dogs with acute lesions).

Conclusions

Directly after treatment, ablation lesions are best evaluated electrophysiologically, because complete (transmural and circumferential) lesions are not shown by histologic evaluation in the acute stage. After 1 to 3 weeks, the histology is in accordance with the electrophysiology. To obtain a complete isolation, online electrophysiologic evaluation during pulmonary vein microwave ablation is necessary to optimize the results.     

The impact on biochemical profiles and allograft function for patients converted from cyclosporine to tacrolimus after clinical heart transplantation

Objective

Tacrolimus, a potent calcineurin inhibitor, is a widely used immunosuppressant. This study sought to determine whether conversion from cyclosporine to tacrolimus afforded benefits on biochemical profiles and graft function among Chinese heart transplantation recipients.

Methods

Forty-nine patients (44 men and 5 women) among 252 heart transplantations performed from 1995 to 2005 were converted from cyclosporine to tacrolimus due to rejection (69%) or to cyclosporine intolerance (31%). The median age of these recipients at transplantation was 46.4 years (range, 5 months to 68 years). Their median body weight was 60 kg (range, 4-84 kg). The allograft median ischemic time was 145 minutes (range, 52-300 minutes). We compared the biochemical markers, rejection episodes and allograft function.

Results

The mean duration from heart transplantation to conversion was 419 days. After conversion, the serum bilirubin and alanine transaminase levels were significantly improved at 1 year. The lipid profiles, including triglycerides, total cholesterol, and low-density lipoprotein were nonsignificantly changed. The rejection episodes significantly decreased from 1.53 to 0.15 per patient per year (P < .001). The left ventricular ejection fraction significantly improved from 54.3 ± 17.9% to 63.2 ± 10.9% (P < .01). The right atrial pressure significantly decreased from 9.1 ± 5.8 mmHg to 6.3 ± 4.3 mm Hg (P < .01). The pulmonary capillary wedge pressure significantly decreased from 15.3 ± 9.5 mm Hg to 10.8 ± 5.3 mm Hg (P = .04).

Conclusion

In heart transplantation, conversion to tacrolimus owing to rejection or cyclosporine intolerance showed better liver profiles with fewer rejection episodes and improved graft function.     

A one-year comparison of prophylactic donor tricuspid annuloplasty in heart transplantation

Background

The bicaval technique for orthotopic heart transplantation decreases the incidence of tricuspid valve regurgitation when compared with the standard biatrial technique. This study was designed to study the effects of prophylactic tricuspid valve annuloplasty during bicaval orthotopic heart transplantation on survival, renal function, and amount of tricuspid valve regurgitation.

Methods

Between April 1997 and March 1998, 60 patients (age 18 to 70 years, 22 women) randomly received either bicaval orthotopic heart transplantation (n = 30) or bicaval orthotopic heart transplantation with DeVega tricuspid valve annuloplasty (n = 30). Tricuspid valve annuloplasty was performed on the donor heart before implantation using pledgeted 2-0 polypropylene suture and sized to an annulus of 29 mm. Echocardiographic variables, laboratory values, and hemodynamics were obtained prospectively and reviewed by an independent data analyst.

Results

Intraoperatively, the group undergoing tricuspid valve annuloplasty had a shorter reperfusion time (46 ± 29 minutes versus 65 ± 48 minutes; p < 0.05) and higher mean pulmonary artery to central venous pressure difference (11.8 ± 3.7 mm Hg versus 15.3 ± 4.1 mm Hg; p = 0.001). Additional differences between the two groups included early mortality from donor dysfunction (4 of 30 patients versus 0 of 30 patients; p < 0.05), amount of tricuspid valve regurgitation at 1 year (1.3 ± 1.0 versus 0.2 ± 0.3; p < 0.05), and percentage of patients with 2+ or greater tricuspid valve regurgitation (34% versus 0%; p < 0.05).

Conclusions

Tricuspid valve annuloplasty of the donor heart before bicaval orthotopic heart transplantation improves immediate donor heart function as demonstrated by better right ventricular performance, lower perioperative mortality, and shorter reperfusion times. At 1 year, there is less tricuspid valve regurgitation but no difference in renal function. Considering the ease and safety of tricuspid valve annuloplasty and its advantages, it should be performed as a routine adjunct with bicaval orthotopic heart transplantation.     

Temporary external DDD pacing after cardiac operations

Temporary atrial and ventricular pacing in the DVI, VVI, and AOO modes using atrioventricular sequential DVI devices is routinely used in cardiac operations. This study evaluated a new temporary external DDD pacemaker (Medtronic 5345 External Pulse Generator) capable of ten pacing modes. Thirty-nine devices have been applied to 38 adult patients (27 male, 11 female) after a variety of open heart procedures. Group 1 had atrial pacing wires placed 1.5 to 2.0 cm apart superiorly on the right atrium, group 2 had atrial wires placed 1.0 to 1.5 cm apart on the right atrial free wall, and group 3 had atrial wires placed on the right atrial free wall 0.8 cm apart, using a Silastic ring for fixation. Ventricular wires were placed on the free wall (group 1) or the diaphragmatic surface (groups 2 and 3) of the right ventricle. Postoperative atrial and ventricular sensing and pacing thresholds were obtained on return to the intensive care unit; analysis of variance demonstrated a significantly greater atrial sensing threshold in group 3. Four patients in group 1 permanently lost atrial sensing, 1 patient in group 2 intermittently lost atrial sensing at 24 hours with return at 36 hours postoperatively, and 1 patient in group 1 lost ventricular sensing capability. All other patients had adequate atrial and ventricular sensing capability documented until elective pacemaker removal (mean, 166 hours; range, 17 to 667.5 hours). Nineteen patients required some form of temporary pacing postoperatively; 11 patients demonstrated hemodynamic benefit from a pacing mode that is not available on the currently used DVI devices, and 7 of these required true DDD pacing capability. Six patients benefited from atrial pacing with adequate atrial sensing and simultaneous ventricular backup. Burst pacing with the device was used successfully to treat postoperative atrial flutter in 2 patients. We conclude that temporary external DDD pacing is feasible and effective in postoperative cardiac surgical patients. Atrial sensing is possible in most patients but electrode positioning is important for adequate thresholds. In some patients, hemodynamic as well as electrophysiologic improvement can be demonstrated with universal DDD pacing capability as compared with standard DVI pacing.     

Intraaortic balloon pumping improves hemodynamics and right ventricular efficiency in acute ischemic right ventricular failure

Background

Left ventricular unloading has a potentially deleterious effect in right ventricular failure as a result of altered septal interplay. However, a positive effect of an intraaortic balloon pump during right ventricular failure has been suggested. We investigated the impact of intraaortic balloon pumping on hemodynamics and both left and right ventricular function in an experimental model of isolated right ventricular failure.

Methods

Sixteen anesthetized pigs (25 to 34 kg) were used in an in vivo model. Pressure-conductance catheters assessed right and left ventricular pressure-volume relationships. Acute right ventricular failure was induced by right coronary microembolization, and led to severely impaired right ventricular function, reduced cardiac output and arterial pressure, and an increased pulmonary vascular resistance and pulmonary arterial elastance. Animals were then randomized to balloon pump or control groups and evaluated with respect to hemodynamics and ventricular function after 1 hour.

Results

Intraaortic balloon pumping did not alter right or left ventricular contractility. However, balloon pump-treated animals had significantly improved cardiac output (+18% ± 18% versus −6% ± 7%; p = 0.003) and mean arterial pressure (+36% ± 30% versus −7% ± 14%; p = 0.004) compared with controls. Animals in the balloon pump group had lower pulmonary vascular resistance (795 ± 63 versus 912 ± 259 dynes · sec · cm⁻⁵; p < 0.01) and pulmonary arterial elastance (1.14 ± 0.20 versus 1.69 ± 0.65 mm Hg/mL; p < 0.01), and increased stroke volume (22.3 ± 4.7 versus 17.9 ± 4.7 mL; p = 0.016). Right ventricular efficiency was also improved in the balloon pump group (stroke work per pressure-volume area = 0.60 ± 0.14 versus 0.41 ± 0.12; p < 0.01).

Conclusions

Intraaortic balloon pump support does not alter right or left ventricular function in acute right ventricular failure. However, arterial pressure, cardiac output, and right ventricular efficiency are improved, possibly because of a balloon pump-induced reduction in pulmonary arterial resistance.     

Incidence of neoplastic disease following lung transplantation: a 17-year single-center experience

Objective

Chronic immunosuppressive therapy following solid organ transplantation has been correlated with an increased risk of posttransplantation neoplastic disease (PTND). In this study we evaluated PTND incidence and outcome at our institution over a 17-year period among patients receiving lung transplantation.

Materials and Methods

Between February 1992 and December 2008, we performed 290 lung transplantations in 280 patients, including 139 single (48% with 5 retransplantations), and 151 double lung transplantations (52% with 5 retransplantations). Among the 280 patients, 2 had undergone previous double lung transplantation in other hospitals. Follow-up of transplant recipients was performed up to December 2009.

Results

Forty-two patients died in the hospital, producing a cumulative early (30-day) mortality rate of 15%. Among the 238 patients discharged from the hospital who entered our follow-up program, 36 (15%) experienced PTND. The mean time between transplantation and diagnosis was 47 ± 42 months, and patients' mean age at time of diagnosis was 55 ± 14 years. Overall freedom from PTND was 97%, 84%, and 73% at 1, 5, and 10 years, respectively. PTND was considered to be the direct cause of death in 11 patients (30%). Overall survival of patients with PTND at five years (45%) did not differ from the remainder of the transplanted population (46%). However, PTND became a relevant cause of death in the long-term (> 5 years) follow-up.

Conclusion

Our experience confirms that PTND was frequently diagnosed following lung transplantation. Even if PTND did not seem to significantly affect the survival of patients undergoing lung transplantation, it may become a significant cause of death among those surviving beyond 5 years.     

Temporary A-V sequential pacing using transluminal pacing electrodes

A case is presented which describes the initiation of atrialventricular (A-V) sequential pacing using atrial epicardial wires and an in situ transluminal ventricular pacing probe. A 68year-old female with a permanent A-V sequential pacemaker was scheduled for elective aortocoronary bypass. Following sternotomy, pacing function was converted to ventricular pacing (WI) with the use of electrocautery. A Chandler® V-pacing probe was introduced through a Paceport® (American Edwards) pulmonary artery catheter and with a paced increase in ventricular rate, the cardiac output increased from 2.8 to 3.2 L · min^-1. At the conclusion of cardiopulmonary bypass the patient was in sinus rhythm at a rate of 67 · min^-1 and was paced to a faster rate using bipolar atrial epicardial wires. The patient subsequently developed intermittent heart block so temporary A-V sequential pacing was established using atrial epicardial wires and the in situ ventricular pacing probe. Pacing was achieved at routine generator output settings of seven milliamps (mA) for both atrium and ventricle and at an A-V interval of 0.120 sec. This resulted in an immediate increase in cardiac output from 3.3 to 4.1L- min^-1. The compatability of these two pacing systems offers an increased margin of safety in cardiac surgery patients requiring atrial pacing, who are at risk for developing postoperative heart block.