Incidence and prognostic value of electrocardiographic abnormalities after heart transplantation

Cardiac Implantable Electronic Devices in Cardiac Transplant Patients: A Comprehensive Review

A fraction of patients (approximately 10%) undergoing heart transplantation require permanent pacemaker (PPM) implantation due to sinus node dysfunction or atrioventricular block, occurring either shortly after surgery or later. The incidence of PPM implantation has declined to less than 5% with the introduction of bicaval anastomosis transplantation surgery. Pacing dependency during follow-up varies among recipients. A smaller subset (1.5-3.4%) receives implantable cardioverter-defibrillators (ICDs), but data on their use in transplant recipients are limited, primarily from cohort studies and case series. Sudden cardiac death affects around 10% of transplant recipients, attributed to various nonarrhythmic factors such as acute rejection, late graft failure, and cardiac allograft vasculopathy-induced ischemia. This review offers a comprehensive analysis of the existing data concerning the role of PPMs and ICDs in this population, encompassing leadless PPMs, subcutaneous ICDs, unique considerations, and future directions.

ECG Features in Orthotopic Cardiac Xenotransplantation: Comparisons With Published Literature

INTRODUCTION

Although there is a plethora of literature on electrocardiographic changes following cardiac allotransplantation, there is little in the field of cardiac xenotransplantation. The only published literature to date is that of the first pig-to-human cardiac xenotransplantation. Here we take a close look at the electrocardiographic parameters in four non-human primate recipients of orthotopic cardiac xenotransplantation to develop baseline metrics for comparison.

METHODS

Orthotopic cardiac xenotransplantion was carried out in four non-human primate recipients. Electrocardiographic parameters were followed at various intervals using an internal hemodynamic monitoring system (DSI) as well as a standard 12-lead electrocardiogram (ECG). ECG intervals were then compared to published literature on porcine ECG intervals and pig-to-human cardiac xenotransplantation.

RESULTS

There were no significant differences observed between timepoints for HR, PR, QRS, QT, or QTc after cardiac xenotransplantation for each animal subject. ECG parameters were statistically similar to those of in situ mini-pig hearts in the literature. ECG parameters from the DSI on average were shorter than those from a traditional ECG, however, DSI parameters were consistent over time.

CONCLUSION

These results demonstrate the possibility of conduction health for genetically engineered porcine donor hearts following cardiac xenotransplantation. Ongoing work to compare the results of an ECG in a porcine donor heart before and after implantation into a NHP is necessary to better characterize variables that may be at play in the function of the conduction system.

Newly acquired complete right bundle branch block early after heart transplantation is associated with lower survival

Aims

Right bundle branch block (RBBB) after heart transplantation (HTX) is a common finding, but its impact on post‐transplant survival remains uncertain. This study investigated the post‐transplant outcomes of patients with complete RBBB (cRBBB) ≤ 30 days after HTX.

Methods

This registry study analysed 639 patients receiving HTX at Heidelberg Heart Center between 1989 and 2019. Patients were stratified by diagnosis of cRBBB ≤ 30 days after HTX. Analysis included recipient and donor data, medication, echocardiographic features, graft rejections, atrial fibrillation, heart rates, permanent pacemaker implantation and mortality after HTX including causes of death.

Results

One hundred thirty‐nine patients showed cRBBB ≤ 30 days after HTX (21.8%), 20 patients with pre‐existing cRBBB in the donor heart (3.2%) and 119 patients with newly acquired cRBBB (18.6%). Patients with newly acquired cRBBB had a worse 1‐year post‐transplant survival (36.1%, P < 0.01) compared with patients with pre‐existing cRBBB (85.0%) or without cRBBB (86.4%), along with a higher percentage of death due to graft failure (P < 0.01). Multivariate analysis indicated cRBBB ≤ 30 days after HTX as significant risk factor for 1‐year mortality after HTX (HR: 2.20; 95% CI: 1.68–2.87; P < 0.01). Secondary outcomes showed a higher rate of an enlarged right atrium (P = 0.01), enlarged right ventricle (P < 0.01), reduced right ventricular function (P < 0.01), 30‐day atrial fibrillation (P < 0.01) and 1‐year permanent pacemaker implantation (P = 0.02) in patients with cRBBB after HTX.

Conclusions

Newly acquired cRBBB early after HTX is associated with increased post‐transplant mortality.

Cardiac Implantable Electronic Devices Following Heart Transplantation

Permanent pacemaker (PPM) implantation is required in a subset of patients (∼10%) for sinus node dysfunction or atrioventricular block both early and late after heart transplantation. The incidence of PPM implantation has decreased to <5% with the advent of bicaval anastamosis transplantation surgery. Pacing dependence upon follow-up has been variably reported. An even smaller percentage of transplantation recipients (1.5% to 3.4%) undergo implantable cardioverter-defibrillator (ICD) placement. Rigorous data are lacking for the use of ICDs in the transplantation population and is largely derived from cohort studies and case series. Sudden cardiac death occurs in approximately 10% of transplantation recipients, but multiple nonarrhythmic factors are believed to be responsible, including acute rejection, late graft failure with electromechanical dissociation, and ischemia due to cardiac allograft vasculopathy. This review provides a comprehensive analysis of the existing data regarding the role for PPMs and ICDs in this population, including leadless PPMs and subcutaneous ICDs, special considerations, and future directions.

Association of Newly Developed Right Bundle Branch Block with Graft Rejection Following Heart Transplantation

PURPOSE

We aimed to examine associations between right bundle branch block (RBBB) following heart transplantation (HT) and graft rejection.

MATERIALS AND METHODS

We investigated 51 patients who underwent endomyocardial biopsies, electrocardiogram, right-side cardiac catheterization, and echocardiography at 1 month and 1 year after HT. We classified patients into four groups according to the development of RBBB, based on electrocardiogram at 1 month and 1 year: 1) sustained RBBB, 2) disappeared RBBB, 3) newly developed RBBB, and 4) sustained non-RBBB. The RBBB was defined as an RSR' pattern in V1 with a QRS duration ≥100 ms on electrocardiogram.

RESULTS

The newly developed RBBB group (n=13, 25.5%) had a higher rate of new onset graft rejection (from grade 0 to grade ≥1R, 30.8% vs. 10.0% vs. 21.4%, p=0.042) at 1 year, compared with sustained RBBB (n=10, 19.6%) and sustained non-RBBB group (n=28, 54.9%). In contrast, the incidence of resolved graft rejection (from grade ≥1R to grade 0) was higher in the sustained RBBB group than the newly developed RBBB and sustained non-RBBB groups (70.0% vs. 7.7% vs. 25.0%, p=0.042). Left atrial volume index was significantly higher in the newly developed RBBB group than the sustained RBBB and sustained non-RBBB groups (60.6±25.9 mL/m² vs. 36.0±11.0 mL/m² vs. 38.4±18.1 mL/m², p=0.003).

CONCLUSION

Close monitoring for new development of RBBB at 1 year after HT, which was associated with a higher incidence of new onset graft rejection, may be helpful to identify high risk patients for graft rejection.

Interventricular conduction disorders after orthotopic heart transplantation: risk factors and clinical relevance

BACKGROUND

Causes and significance of interventricular conduction disorders (IVCDs) after orthotopic heart transplantation (OHT) are still unknown.

METHODS

We retrospectively researched the presence of IVCDs in 240 patients who underwent bicaval OHT in three time periods: at day 1, after 1 year, and after 3 years from OHT. To evaluate the impact of the surgical technique, a control population treated with biatrial anastomosis was used.

RESULTS

The most common IVCD was right bundle branch block (RBBB). Its presence at day 1 correlated with transpulmonary gradient before OHT. Its presence after 1 year and its development correlated with a 1-month acute rejection score≥2 (p = .050 and p = .006). The incidence of RBBB was higher in the biatrial control population (40.7% vs 23.8%, p < .001).

CONCLUSIONS

RBBB is the most common IVCD. Its presence can be explained by a susceptibility of the right branch to heart positioning, pressure overload, and acute rejection. IVCDs do not affect prognosis.

Electrocardiographic abnormalities in the first year after heart transplantation

STUDY AIM

Describe ECG abnormalities in the first year following transplant surgery.

METHODS

Analysis of 12-lead ECGs from heart transplant subjects enrolled in an ongoing multicenter clinical trial.

RESULTS

585 ECGs from 98 subjects showed few with abnormal cardiac rhythm (99% of ECGs were sinus rhythm/tachycardia). A majority of subjects (69%) had either right intraventricular conduction delay (56%) or right bundle branch block (13%). A second prevalent ECG abnormality was atrial enlargement (64% of subjects) that was more commonly left atrial (55%) than right (30%).

CONCLUSIONS

Right intraventricular conduction delay or right bundle branch block is prevalent in heart transplant recipients in the first year following transplant surgery. Whether this abnormality is related to acute allograph rejection or endomyocardial biopsy procedures is the subject of the ongoing clinical trial. Atrial enlargement ECG criteria (especially, left atrial) are also common and are likely due to transplant surgery with subsequent atrial remodeling.

Cardiac electrophysiology in mice: a matter of size

Over the last decade, mouse models have become a popular instrument for studying cardiac arrhythmias. This review assesses in which respects a mouse heart is a miniature human heart, a suitable model for studying mechanisms of cardiac arrhythmias in humans and in which respects human and murine hearts differ. Section I considers the issue of scaling of mammalian cardiac (electro) physiology to body mass. Then, we summarize differences between mice and humans in cardiac activation (section II) and the currents underlying the action potential in the murine working myocardium (section III). Changes in cardiac electrophysiology in mouse models of heart disease are briefly outlined in section IV, while section V discusses technical considerations pertaining to recording cardiac electrical activity in mice. Finally, section VI offers general considerations on the influence of cardiac size on the mechanisms of tachy-arrhythmias.

Reversible abnormality of electrocardiogram as a sign of acute cardiac rejection after orthotropic heart transplantation

Cardiac allograft rejection can be accompanied by diastolic dysfunction, but the hemodynamic change is usually compensated and hard to be recognized noninvasively. Here we report on two transplanted patients who showed electrocardiogram (ECG) changes suggesting right ventricular overload. Hemodynamic measurement revealed increased right ventricular pressure and endomyocardial biopsy confirmed grade 3R rejection. After rejection was treated with steroid pulse, the ECG alterations were reversed and right ventricular pressure was normalized. In such cases, asymptomatic rejection may be diagnosed by ECG changes that are reversible along with the treatment of rejection, although those ECG changes are apparently non-specific.

Intensivtherapie nach Organtransplantation

Nach langen Diskussionen bietet das Transplantationsgesetz, das seit 01.12.1997 in Kraft ist, Rechtssicherheit. Das Gesetz dient dem Schutz des Spenders und des Empfängers, und es bietet Rechtssicherheit für alle in der Transplantationsmedizin Tätigen. Das Gesetz legt die Rechte und Verpflichtungen der Beteiligten und die Wege der Organspende und -vermittlung fest. Das Gesetz unterscheidet zwischen der Organentnahme bei Lebenden und bei Verstorbenen und legt die Rahmenbedingungen fest. Die Umsetzung der Todesbestimmung soll nach den Erkenntnissen der medizinischen Wissenschaft erfolgen und ist in den Richtlinien der Bundesärztekammer (3. Fortschreibung 1997) festgelegt worden.

Prevalence, patterns of development, and prognosis of right bundle branch block in heart transplant recipients

Right bundle branch block (RBBB) is the most common electrocardiographic abnormality in heart transplant recipients, but the cause remains unknown, data regarding the prognosis are conflicting, and all previous studies have been limited to <100 patients. This was a study of patients who underwent heart transplantation at Stanford University Medical Center from 1981 to 1995 with known outcomes and >or=2 available electrocardiograms (ECGs). Outcomes were assessed in those with and without conduction disturbances recorded from the ECGs closest to the time of transplantation and the most recent ECGs. Of the 322 heart transplant recipients studied, 141 (44%) died over a mean follow-up of 9 +/- 3.5 years, and 40 (13%) died of sudden cardiac death. In the first ECG obtained, a mean of 1.8 +/- 2.4 years after transplantation, 44 patients (14%) had incomplete RBBB and 26 (8%) had RBBB; in the second ECG, obtained a mean of 5.6 +/- 3.7 years after transplantation, 59 patients (18%) had incomplete RBBB and 63 (20%) had RBBB. Increasing time from transplantation was associated with a greater likelihood for RBBB on the first and second ECGs (p = 0.001 and p <0.0001, respectively). QRS duration, incomplete RBBB, RBBB, or the development of RBBB was not associated with mortality or sudden cardiac death. In conclusion, although RBBB was the most common electrocardiographic abnormality in our study, the prevalence was lower than previously reported. The cause of RBBB appears to be largely related to events that occur well after transplantation, and the prognosis is benign.

Efficacy of signal-averaged electrocardiography in the young orthotopic heart transplant patient to detect allograft rejection

Endomyocardial biopsy is the gold standard survey for cardiac graft rejection. Signal-averaged electrocardiography (SAECG) identifies slowly conducting, diseased myocardium. We sought to determine whether SAECG is a sensitive, noninvasive transplant surveillance method in the young.Ninety-four SAECGs recorded prior to biopsy in 20 young transplant (OHT) patients and those from 15 healthy age-matched controls (CTL) were analyzed. In the OHT group, 56 no-rejection (NOREJ) (ISHLT grades 0 or 1 A) and 37 acute rejection (REJ) (ISHLT grades IB, 2, and 3A) SAECGs were compared, SAECGs were filtered at 40-255 Hz. Total QRS duration (QRSd), duration of terminal low amplitude of QRS under 40 microV (LAS), and root mean square amplitude of terminal 40 msec of QRS (RMS40) were compared.SAECGs were significantly different in CTL vs NOREJ but not in NOREJ vs REJ: QRSd, 81.7 +/- 8, 107.2 +/- 18.4, and 112.3 +/- 21.6 msec, respectively; LAS, (18 +/- 5.8, 23.6 +/- 10.7, and 27 +/- 14.8 msec, respectively; and RMS40, (169.3 +/- 100.4, 68 +/- 48.8, and 57.5 +/- 45.6 microV, respectively. Children following OHT exhibited significant differences in the SAECG compared to controls. Differences between the NOREJ and REJ groups were negligible. Therefore, SAECG may not be effective in detecting OHT rejection in the young.

Arrhythmias after orthotopic heart transplantation

BACKGROUND

Arrhythmias frequently occur after orthotopic heart transplantation (OHT).

METHODS AND RESULTS

The most common are ventricular premature complexes, atrial premature complexes, sinus or junctional bradycardia, atrial fibrillation, and atrial flutter, all of which have varying clinical significance depending on associated or causative conditions. Unique etiologic factors such as allograft rejection, transplant coronary artery disease, and altered anatomy and autonomic nervous system changes require that arrhythmias be treated differently after OHT compared with the general population.

CONCLUSION

The potentially severe ramifications of allograft rejection and coronary artery disease make treatment of these disorders in the setting of arrhythmias as important as treating the arrhythmias themselves. At the same time, autonomic denervation and altered anatomy after transplantation complicate drug and device therapies.

Electrocardiographic changes simulating a myocardial infarction after cardiac transplantation

A 39-year-old man with idiopathic dilated cardiomyopathy and New York Heart Association Class III heart failure symptoms underwent orthotopic cardiac transplantation. Post-operatively, he developed an anteroseptal infarct pattern on the electrocardiogram (ECG), without regional wall motion abnormalities according to echocardiography. This pseudo-infarct pattern on ECG resolved within 6 months without coronary intervention or sequelae. It is postulated that these ECG changes were caused by increased left ventricular wall thickness due myocardial wall edema and reperfusion injury after cardiac transplantation.

Long-term follow-up of arrhythmias in pediatric orthotopic heart transplant recipients: incidence and correlation with rejection

BACKGROUND

Arrhythmias in adult orthotopic heart transplant (OHT) recipients are common and have been used as predictors of rejection. Because of the paucity of information in pediatric OHT recipients, the purpose of this study was to determine the incidence and correlation of arrhythmias with rejection or with coronary artery disease (CAD) in children.

METHODS

We retrospectively reviewed the records, electrocardiograms (ECGs), and 24-hour ambulatory ECGs of patients who underwent OHT from January 1984 to December 1999. We excluded arrhythmias occurring in the first 2 weeks after OHT.

RESULTS

Sixty-nine patients underwent OHT, received triple-immunosuppression therapy, were discharged home, and have been followed for a mean of 4.7 years (0.3-13 years). Each patient had an average of 10 ECGs and three 24-hour ECGs. Twenty-six patients had 33 arrhythmias: sinus bradycardia (n = 9), atrial tachycardia (n = 9), ventricular tachycardia (n = 3), and Wenckebach periodicity (n = 6). Sinus bradycardia was treated with theophylline in 8 patients, and 2 required pacemakers. Atrial tachycardias (atrial flutter in 4 patients and atrial ectopic tachycardia in 5) were treated with digoxin, propranolol, or procainamide. Ventricular tachycardia was treated with mexiletine, lidocaine, and amiodarone. There were 65 episodes of rejection, 20 of which were moderate/severe (> or =3B). Only Wenckebach was associated with the presence of either rejection or CAD (p < 0.05).

CONCLUSIONS

We noted clinically significant arrhythmias in 38% of the pediatric OHT recipients. Sinus bradycardia, atrial tachyarrhythmias, and ventricular tachycardia occurred with the same frequency. Only new-onset Wenckebach periodicity was noted in the presence of either CAD or rejection. No arrhythmia was of negative predictive value for rejection or CAD. From this data, we suggest that new-onset Wenckebach prompt evaluation for rejection or CAD.

Impaired conduction in the bundle branches of mouse hearts lacking the gap junction protein connexin40

BACKGROUND

Connexin (Cx)40 and Cx45 are the major protein subunits of gap junction channels in the conduction system of mammals. To determine the role of Cx40, we correlated cardiac activation with Connexin distribution in normal and Cx40-deficient mice hearts.

METHODS AND RESULTS

Epicardial and septal activation was recorded in Langendorff-perfused adult mice hearts with a 247-point compound electrode (interelectrode distance, 0.3 mm). After electrophysiological measurements, hearts were prepared for immunohistochemistry and histology to determine Connexin distribution and fibrosis. In both wild-type and Cx40-deficient animals, epicardial activation patterns were similar. The right and left ventricular septum was invariably activated from base to apex. Histology revealed a continuity of myocytes from the common bundle to the septal myocardium. Within this continuity, colocalization was found of Cx43 and Cx45 but not of Cx40 and Cx43. Both animals showed similar His-bundle activation. In Cx40-deficient mice, the proximal bundle branches expressed Cx45 only. The absence of Cx40 in the proximal bundles correlated with right bundle-branch block. Conduction in the left bundle branch was impaired as compared with wild-type animals.

CONCLUSIONS

Our data show that (1) in mice, a continuity exists between the common bundle and the septum, and (2) Cx40 deficiency results in right bundle-branch block and impaired left bundle-branch conduction.