Use of percutaneous transluminal septal myocardial ablation for relief of outflow tract obstruction in cardiac amyloidosis: a novel therapeutic target.

Cardiac amyloidosis typically presents with diastolic heart failure, but asymmetrical septal hypertrophy with outflow tract obstruction has been described. We illustrate the case of a 71-year-old woman with biopsy-proven cardiac amyloidosis and severe medical comorbidities with refractory severe heart failure who had asymmetric septal hypertrophy, systolic anterior motion (SAM) of the mitral valve, and a resting left ventricular outflow tract gradient of 86 mm Hg, increasing to 102 mm Hg on Valsalva maneuver. She underwent percutaneous transluminal septal myocardial ablation (PTSMA) with a dramatic resolution of her SAM and outflow tract obstruction, confirmed by intracavitary pressure wire measurements. PTSMA is technically feasible in this context, and correction of outflow tract obstruction may represent a new therapeutic target in cardiac amyloidosis.

Plexiform pigmented schwannoma of the uvea.

Schwannoma is a slow growing solitary tumor that preferentially involves spinal nerve roots, and sympathetic, cervical, and vagus nerves. There are several clinico-pathologic variants of schwannoma, including schwannoma with a degenerative change (ancient schwannoma), cellular schwannoma, plexiform schwannoma, epithelioid schwannoma, and melanotic schwannoma. About 10% of cases of schwannomas are associated with multi-system disorders such as neurofibromatosis, schwannomatosis, multiple meningiomas, and Carney complex. Schwannoma rarely present as an intraocular tumor and is often misdiagnosed as malignant melanoma. Immunohistochemical positivity with S-100 stain and demonstration of long-spaced collagen (Luse bodies) are helpful in establishing the diagnosis. In this article, we review the clinical and histopathological findings of a sporadic plexiform pigmented schwannoma involving the iris, ciliary body, and the choroid.

The impact of donor gender on cardiac peri-transplantation ischemia injury.

BACKGROUND: Cardiac allografts from female donors have been shown to be associated with increased risk of transplant vasculopathy. However, the influence of donor gender on peri-transplantation ischemic injury has not been evaluated. METHODS: A total of 361 patients (mean age, 52 +/- 10 years) underwent cardiac transplantation between January 1998 and December 2002. Patients were divided into 4 groups according to their donor-recipient gender status: Group A, male-male, 156; Group B, male-female, 37; Group C, female-male, 114; and Group D, female-female, 54. Serial right ventricular endomyocardial biopsy specimens were evaluated for ischemic injury during the first 4 weeks after transplantation. RESULTS: Patients were similar in baseline characteristics. An increased incidence of ischemic injury complicated by fibrosis (12.9%, p = 0.03) and subsequent development of transplant vasculopathy (Kaplan-Meier 6-year freedom from vasculopathy, 53.4%; p = 0.012) was noted in Group D. No survival difference was observed among the 4 groups, however. In Group D (F-F), 2 patients underwent retransplantation and 2 patients underwent revascularization. CONCLUSIONS: The transplantation of a female cardiac allograft into a female recipient is associated with increased risk of ischemic injury complicated by fibrosis and subsequent transplant vasculopathy.

The impact of CytoGam on cardiac transplant recipients with moderate hypogammaglobulinemia: a randomized single-center study.

BACKGROUND: We have previously shown that the preemptive use of cytomegalovirus (CMV) immunoglobulin (Ig) replacement (CytoGam) decreases the incidence of opportunistic infections in cardiac transplant recipients with severe hypogammaglobulinemia. However, the impact of Ig replacement in moderately hypogammaglobulinemic patients is unknown. METHODS: Periodic monitoring of the IgG levels was done in 300 heart transplant recipients. Moderate hypogammaglobulinemia (IgG, 350-500 mg/dl) developed in 56 patients (18.6%). Thirty-three patients declined randomization but agreed to have their IgG levels monitored. Twenty-three patients were randomized to placebo (n = 10) or CytoGam (n = 13) at 105 +/- 63 days after transplantation. RESULTS: The baseline characteristics were similar. A significant reduction in CMV infection was noted in the CytoGam Group compared with the Placebo Group (15.4% [2/13] vs 60% [6/10], p = .039). Among patients who declined randomization, CMV infection developed in 13 (39.4%) of 33, and 6 (46.1%) of the 13 progressed to severe hypogammaglobulinemia. A trend for reduction in the average episodes of > or =grade 2 rejection during the 6-month period after randomization was noted in the CytoGam group (0.4 +/- 0.6 vs 1.4 +/- 1.3, p = 0.065). CONCLUSIONS: The preemptive use of CytoGam decreases the incidence of CMV infection in patients with moderate hypogammaglobulinemia. A larger randomized study is needed to substantiate these results.

Small intestinal submucosa intracardiac patch: an experimental study.

In this experimental study, small intestinal submucosa was implanted as an atrial prosthesis in calves. Echocardiography and histology showed this to be an impermeable prosthesis that develops a neointimal nonthrombogenic surface making it safe for repair of defects in a low-pressure system. Further study with small intestinal submucosa in an intracardiac position is warranted.

Peritransplant ischemic injury is associated with up-regulation of stromal cell-derived factor-1.

OBJECTIVES: We evaluated chimerism and stromal cell-derived factor-1 (SDF-1) expression in response to peritransplant ischemic injury following human heart transplantation. BACKGROUND: Myocardial ischemia has been shown to trigger mobilization of stem cells to the heart in animal experiments. METHODS: Between January 1998 and April 2002, a total of 114 male recipients received hearts from female donors. Of these 114 recipients, 26 had evidence of ischemic injury on their initial heart biopsies (ischemia group). These were compared to the remaining 88 patients (control group). Heart biopsy specimens obtained initially at one week and at one year after transplant were evaluated from 20 matched patients of each group for the presence of Y chromosome-containing nuclei. The SDF-1 messenger ribonucleic acid (mRNA) and protein expression were also evaluated on initial heart biopsy specimens. RESULTS: At one week, Y chromosome-containing nuclei were significantly increased in the ischemia group (0.68% vs. 0.04%; p < 0.0001) compared to the control group. These were positive for the stem cell factor receptor c-kit. A significant 3.3-fold increased mRNA expression (p = 0.001) and 2.8-fold increased protein expression (p = 0.01) of SDF-1 was noted in the ischemia group. At one year, Y chromosome was detected in 0.29% of cardiomyocyte nuclei in the ischemia group but none in the control group. The ischemia group had poorer survival and increased vasculopathy. CONCLUSIONS: This is the first report to describe chimerism and up-regulation of SDF-1 in human heart transplantation in response to ischemic injury.

Systemic activation of integrin alphaVbeta3 in donors with spontaneous intracerebral hemorrhage is associated with subsequent development of vasculopathy in the heart transplant recipient.

BACKGROUND: Recipients of hearts from donors with spontaneous intracerebral hemorrhage (ICH) are at increased risk of allograft vasculopathy compared with trauma donors. We have recently shown that the vitronectin receptor (integrin alpha(V)beta3) is upregulated in transplant vasculopathy. We hypothesized that donor ICH is associated with systemic activation of alpha(V)beta3 in the donor before transplantation. METHODS: We evaluated mRNA expressions of alpha(V)beta3 (TaqMan PCR) in endomyocardial biopsy samples at 1-week post-transplant in 20 recipients from ICH donors and 20 recipients from trauma donors. To investigate whether systemic activation of alpha(V)beta3 was present in the donor before transplantation, alpha(V)beta3 expression was also evaluated in the corresponding donor spleen lymphocytes. All patients underwent serial coronary intravascular ultrasound to evaluate for coronary vasculopathy. The baseline characteristics were similar except for increased donor age in the ICH Group. RESULTS: The ICH Group showed significant increased mRNA expression of alpha(V)beta3 in the heart biopsy samples (3.8-fold, p = 0.012) and in the corresponding donor spleen lymphocytes (3.5-fold, p = 0.014) compared with the Trauma Group. At 1 year, the ICH Group also showed increased progression of coronary vasculopathy. Multivariate regression analysis found that donor lymphocytic alpha(V)beta3 mRNA expression was independently associated with increased risk of vasculopathy (odds ratio, 1.9; 95% CI, 1.21-3.98, p = 0.03). CONCLUSIONS: Our report demonstrates the presence of systemic activation of alpha(V)beta3 in donors with spontaneous intracerebral hemorrhage and its association with the subsequent development of allograft vasculopathy in the recipient.

Lack of usefulness of electron beam computed tomography for detecting coronary allograft vasculopathy.

Fifty-five patients with cardiac allografts were studied by electron beam computed tomography for coronary calcification (EBCT CC) and coronary arteriography, and from the latter, a coronary index was calculated using the size, degree of obstruction, and linear extent of disease of each vessel. There was a significant correlation between EBCT CC score and coronary index, but receiver-operating characteristic (ROC) analysis demonstrated unsatisfactory performance of EBCT CC, and 6 patients had no coronary calcification despite having very abnormal coronary indexes. There are pathologic differences between coronary allograft vasculopathy and atherosclerosis, and correspondingly, EBCT CC has limited usefulness in the cardiac transplant population.

Biomechanical and echocardiographic characterization of flail mitral leaflet due to myxomatous disease: further evidence for early surgical intervention.

BACKGROUND: Flail mitral leaflet (FML) is a common complication of mitral valve prolapse, often leading to severe mitral regurgitation (MR) and left ventricular dysfunction. In the absence of timely surgical correction, survival is significantly impaired. Early recognition of FML and identification of risk factors is important because early intervention increases the chances of survival. METHODS: We studied 123 patients undergoing mitral valve surgery for severe MR caused by myxomatous disease. Chart review, echocardiography, and tensile testing were performed. RESULTS: Thirty-eight patients had FML, and 85 patients had non-flail mitral leaflet (non-FML). Patients with FML were younger (53.7 +/- 1.8 vs 59.3 +/- 1.4 years, P =.02), had more severe MR (3.89 +/- 0.04 vs 3.76 +/- 0.04, P =.02), were less likely to be in New York Heart Association class III or IV heart failure (5% vs 20%, P =.037), and were less likely to have bileaflet mitral valve prolapse (5% vs 38%, P <.001) than non-FML patients. Valve tissue from patients with FML had less stiff chordae (23.5 +/- 3.6 vs 59.1 +/- 11.7 Mpa, P =.006) that tended to have a lower failure stress (3.8 +/- 0.9 vs 9.6 +/- 2.2 Mpa, P =.07) and had more extensible leaflets (56.4% +/- 7.9% vs 42.9% +/- 2.7% strain, P =.04) compared with that of non-FML patients. CONCLUSIONS: The development of FML may result from intrinsic tissue abnormalities and is associated with a distinct subset of the myxomatous population. Identification of such clinical characteristics in this population and knowledge of an implicit mechanical abnormality of valve tissue may further the argument for early surgical correction.

Systemic up-regulation of angiotensin II type 1 receptor in cardiac donors with spontaneous intracerebral hemorrhage.

Donor spontaneous intracerebral hemorrhage (ICH) is a potential risk factor for morbidity and mortality after cardiac transplantation. We hypothesized that donor ICH is associated with systemic up-regulation of angiotensin II receptor type 1 (AT1R). We evaluated mRNA expression of AT1R and AT2R in donor spleen lymphocytes and in heart biopsies from 20 recipients of hearts from donors with spontaneous ICH which were compared with 20 recipients from trauma donors. Heart biopsies showed 4.7-fold increased mRNA expression of AT1R (p < 0.0001) in the ICH group compared with the Trauma group. The ICH group also showed 2.6-fold (p < 0.01) increased mRNA expression of AT1R in the donor spleen lymphocytes, suggesting the presence of systemic activation before transplantation. At 1 year, the ICH group had increased coronary vasculopathy by vascular ultrasound. Using multivariate regression analysis, mRNA expression of AT1R in the donor spleen lymphocytes was found to be a strong independent predictor of transplant vasculopathy (odds ratio = 4.397, CI = 1.243-15.553, adjusted p = 0.02). This is the first report to describe splenic up-regulation of AT1R in the presence of spontaneous ICH and its association with subsequent development of transplant vasculopathy.

Angiotensin II receptors from peritransplantation through first-year post-transplantation and the risk of transplant coronary artery disease.

OBJECTIVES: We evaluated whether the angiotensin II (Ang II) receptors from perioperation through one-year post-transplantation predict the transplant coronary artery disease (TCAD) progression. BACKGROUND: The role of Ang II receptors (type 1: AT(1)R; type 2: AT(2)R) in TCAD is uncertain. METHODS: We investigated 28 heart donors and the corresponding recipients. The levels of AT(1)R and AT(2)R messenger ribonucleic acid (mRNA) were examined in lymphocytes from the donor spleen and in the donor heart at one-week and one-year posttransplantation to determine their association with the progression of TCAD, measured as changes in maximal intimal thickness (CMIT) and plaque volume (CPV) by intravascular ultrasound (IVUS) examinations. RESULTS: The AT(1)R mRNA in lymphocytes from the donor spleen (CMIT: r = 0.73, p < 0.0001; CPV: r = 0.69, p < 0.0001) and in the donor hearts at one-week (CMIT: r = 0.52, p = 0.005; CPV: r = 0.56, p = 0.002) and at one-year (CMIT: r = 0.63, p < 0.0001; CPV: r = 0.43, p = 0.004) post-transplantation along with AT(2)R mRNA in the donor hearts at one-year post-transplantation (CMIT: r = 0.3, p < 0.0001; CPV: r = 0.53, p = 0.009) were univariate predictors, whereas AT(1)R mRNA in lymphocytes and in the donor hearts at one-year post-transplantation proved to be multivariate predictors of the progression of TCAD. CONCLUSIONS: These data suggest a role for Ang II receptors in the pathogenesis of TCAD and support a novel concept that TCAD may have its origin in the donor per se and may be modulated by the recipient's inherent biological factors.

Cardiac angiotensin II receptors as predictors of transplant coronary artery disease following heart transplantation.

AIMS: We tested the hypothesis that cardiac angiotensin II (Ang II) receptor gene transcription may predict the development of transplant coronary artery disease (TCAD) following heart transplantation. METHODS AND RESULTS: We examined the gene transcripts of Ang II type 1 (AT1R) and type 2 receptors (AT2R) in endomyocardial biopsy specimens from 50 heart transplant recipients. The progression of TCAD was measured as change in maximal intimal thickness (CMIT) and change in plaque volume (CPV) by intravascular ultrasound (IVUS) examinations from baseline to one year after transplantation. The development of transplant vasculopathy was defined as a CMIT of > or = 0.3 mm over one year. The level of AT(1)R mRNA was associated with that of AT2R in transplanted hearts (regression coefficient=1.77, 95% CI 0.85-2.89, p<0.0001). AT1R and AT2R gene transcripts were univariate predictors of CMIT (AT1R: regression coefficient 0.10, 95% CI 0.06-0.14, p<0.0001; AT2R: regression coefficient 0.28, 95% CI 0.17-0.40, p<0.0001 ) or CPV (AT1R: regression coefficient 0.41, 95% CI 0.17-0.65, p<0.0001 ; AT2R: regression coefficient 1.25, 95% CI 0.49-2.01, p=0.002 ). By one year, 21 (46%) transplant recipients showed evidence of transplant vasculopathy and the rest did not. The vasculopathic group demonstrated a higher level of expression of cardiac AT1R than the non-vasculopathic group (3.7+/-2.9 vs 1.6+/-1.7 folds; p=0.006). The level of AT(1)R mRNA in transplanted heart was identified as a discriminator that predicted the development of transplant vasculopathy with a sensitivity of 75% and specificity of 83%. CONCLUSIONS: Cardiac Ang II receptor gene transcripts are associated with the progression of TCAD following heart transplantation. Only AT1R gene transcripts predicted the development of transplant vasculopathy in this preliminary study. These findings potentially support a role of Ang II receptors in the progression of TCAD following cardiac transplantation.

Does acute cellular rejection correlate with cardiac allograft vasculopathy?

BACKGROUND: Previous studies of the association between acute cellular rejection and cardiac allograft vasculopathy (CAV) have yielded conflicting conclusions. We explored a possible association between acute cellular rejection and the extent of CAV, and we found a potential confounding variable that may obscure such an association. METHODS: We investigated 140 patients (mean age, 51 +/- 11 years) who underwent serial intravascular ultrasound examinations at baseline and at 1 year after heart transplantation to assess CAV as change in maximal intimal thickness (CMIT). Patients were classified according to the presence or absence of biopsy-proven myocardial fibrosis. We used a standard biopsy-scoring system and a novel biopsy-scoring system, developed in our institution, to assess acute cellular rejection. Using univariate analysis, we found that CMIT was not associated with acute cellular rejection in the overall patient population (n = 140). However, we observed a correlation between CMIT and acute cellular rejection (standard method, r = 0.30, p = 0.01; novel method, r = 0.51, p < 0.0001) in patients who had no evidence of ischemic injury or fibrosis in their biopsy specimens (n = 57). Step-wise multiple regression showed that the rejection score derived from our novel method was associated more closely with the CMIT than was that derived from the traditional method. CONCLUSIONS: This data indicate that the presence of myocardial fibrosis masks an actuarial association between acute cellular rejection and the development of de novo allograft vasculopathy. As previously suspected, myocardial fibrosis is a marker for non-immune-mediated graft injury independently associated with an increased incidence of CAV.

Donor hepatitis-C seropositivity is an independent risk factor for the development of accelerated coronary vasculopathy and predicts outcome after cardiac transplantation.

BACKGROUND: It is possible, but unproven, that hepatitis C (HCV) infection accelerates atherosclerosis. We evaluated the hypothesis that donor HCV seropositivity predicts mortality and the development of coronary vasculopathy in cardiac transplant recipients. METHODS: Thirty-four cardiac transplant recipients who were seronegative for HCV at the time of transplantation received hearts from HCV-seropositive donors. We compared the mortality and the incidence of vasculopathy in this group of patients (study group) with a group of 183 successive heart transplant recipients (control group) with no evidence of HCV in the donor or in the recipient. RESULTS: After transplantation, 75% of the HCV-seronegative patients who received hearts from HCV-seropositive donors had detectable and persistent viremia (presence of HCV-RNA by reverse-transcription polymerase chain reaction). After a mean follow-up of 4.2 +/- 1.9 years, mortality was 2.8-fold greater in the study group than in controls (95% confidence interval [CI], 1.3-5.7; p = 0.006). The risk of having any vasculopathy after a mean follow-up of 3.4 +/- 1.6 years and after adjustment for other significant risk factors was 3-fold greater (hazards ratio, 3.08; 95% CI 1.52-6.20; p = 0.001) in the HCV group compared with controls. The risk of developing advanced vasculopathy was much greater in the study group compared with controls (hazard ratio, 9.4; 97% CI, 3.3-26.6; p = < 0.0001). The risk of mortality (p = 0.005) and vasculopathy (p = < 0.0001) was greatest in patients with combined donor HCV seropositivity and the presence of antibodies against donor B cells by flow cytometry. CONCLUSION: We conclude that donor hepatitis-C virus seropositivity is an independent risk factor for increased mortality and for the development of accelerated allograft vasculopathy after cardiac transplantation. These observations may have implications for the use of HCV-positive donors in heart transplant recipients.

Impact of donor spontaneous intracranial hemorrhage on outcome after heart transplantation.

Donor cause of death has been suggested to have a significant impact on cardiac transplant morbidity and mortality. Our objective was to evaluate the impact of donor spontaneous intracranial bleeding on clinical outcome after heart transplantation. A group of 160 recipients underwent cardiac transplantation from donors with spontaneous intracranial bleeding (ICB group). These were compared with 197 recipients who were transplanted from trauma donors (Trauma group). A higher 4-year mortality rate was noted in the ICB group (24% vs. 14%, p=0.015). ICB as a cause of donor death was an independent predictor of recipient mortality (adjusted hazard ratio 2.02, 95% CI 1.27-3.40, p<0.0001). Compared with the Trauma group, the ICB group had an increased incidence of post-transplant graft dysfunction during the first week of transplant (10% vs. 3%, p=0.007), and higher incidence of interstitial myocardial fibrosis on their endomyocardial biopsies within 4 weeks of transplant (21% vs. 9%, p=0.0012). There was a trend towards an increased rate of allograft vasculopathy in the ICB group (competing risks adjusted hazard ratio 1.39, 95% CI 0.90-2.13, p = 0.14).

Surgical management of conjunctival lymphangiectasis by conjunctival resection.

PURPOSE: To report the treatment of symptomatic conjunctival lymphangiectasis with conjunctival resection. DESIGN: Interventional case series. METHODS: Retrospective review of three cases of patients with symptomatic unilateral conjunctival lymphangiectasis who had conjunctival resection of the involved tissue down to bare sclera. RESULTS: The surgical area reepithelialized without recurrence of the lymphatics. In all cases the patients have remained asymptomatic for at least 14 months. CONCLUSION: Conjunctival resection for symptomatic lymphangiectasis can be a successful therapeutic option for this condition.

Donor spontaneous intracerebral hemorrhage is associated with systemic activation of matrix metalloproteinase-2 and matrix metalloproteinase-9 and subsequent development of coronary vasculopathy in the heart transplant recipient.

BACKGROUND: Matrix metalloproteinase (MMP)-2 and MMP-9 have been shown to play a role in the progression of hemorrhagic stroke. We hypothesized that donor intracerebral hemorrhage (ICH) is associated with activation of the metalloproteinases before transplantation that play a key role in the subsequent development of transplant vasculopathy. METHODS AND RESULTS: We evaluated mRNA expressions of MMP-2 and MMP-9 in donor spleen lymphocytes (before transplantation) and in heart biopsies at 1 week after transplantation in 20 recipients from ICH donors and 20 recipients from trauma donors. Patients underwent serial coronary intravascular ultrasound, and interstitial myocardial fibrosis was quantified at 1 year. The baseline characteristics were similar except for increased donor age in the ICH group. Heart biopsies from the ICH group showed significant increased expression of MMP-2 (17-fold, P<0.0001) and MMP-9 (20-fold, P<0.0001) compared with the trauma group. Furthermore, the ICH group showed 1.8-fold (P=0.016) increased mRNA expression of MMP-2 and 1.7-fold (P=0.015) increased mRNA expression of MMP-9 in the donor spleen lymphocytes, suggesting the presence of systemic activation of metalloproteinases before transplantation. At 1 year, the ICH group showed increased myocardial fibrosis and accelerated coronary vasculopathy. Using multivariate regression analysis, MMP-9 was found to be associated with increased risk for vasculopathy independent of donor age (OR, 2.41; P=0.01; 95% CI, 1.24 to 4.69). CONCLUSIONS: This is the first report to describe systemic activation of MMP-2 and MMP-9 in donors with intracerebral hemorrhage and subsequent development of allograft vasculopathy.

Sustained apoptosis in human cardiac allografts despite histologic resolution of rejection.

BACKGROUND: We investigated the occurrence of apoptosis during and after resolution of cardiac allograft rejection. Apoptosis could play different roles in graft survival depending on the target cells; thus, we also determined the cell types involved. METHODS: Endomyocardial biopsy specimens were evaluated during the first 6 months after transplantation as follows: group I, no current or prior rejection; group II, during an episode of moderate rejection; and group III, histologic resolution after an episode of moderate rejection. RESULTS: Groups II and III showed significantly increased apoptotic activity, indicated by increased caspase-8 and caspase-3 activity; however, activated caspase-3 was undetectable in group I. Activated caspase-3 was detected only in groups II and III. Terminal deoxynucleotide transferase-mediated dUTP nick-end labeling was detected in groups II and III but not group I and predominantly in inflammatory cells. CONCLUSIONS: Increased caspase activity and apoptosis of infiltrating cells not only occurs during acute cardiac allograft rejection but persists after histologic resolution. Thus, programmed cell death occurs beyond the period of histologic resolution and may play a role in regulation of the rejection process.

Evidence of specialized conduction cells in human pulmonary veins of patients with atrial fibrillation.

UNLABELLED: Specialized Conducting Cells in Human PV. INTRODUCTION: Depolarizations similar to those from the sinus node have been documented from the pulmonary veins after isolation procedures. We assessed the hypothesis that sinus node-like tissue is present in the pulmonary veins of humans. METHODS AND RESULTS: Pulmonary vein tissue was obtained from five autopsies (four individuals with a history of atrial fibrillation and one without a history of atrial arrhythmias) and five transplant heart donors. Autopsy veins were fixed in formaldehyde and processed for light microscopy to identify areas having possible conductive-like tissue. Areas requiring additional study were extracted from paraffin blocks and reprocessed for electron microscopy. Donor specimens were fixed in formaldehyde for histologic sections and glutaraldehyde for electron microscopy. Myocardial cells with pale cytoplasm were identified by light microscopy in 4 of the 5 autopsy subjects. Electron microscopy confirmed the presence of P cells, transitional cells, and Purkinje cells in the pulmonary veins of these cases. CONCLUSION: Our report is the first to show the presence of P cells, transitional cells, and Purkinje cells in human pulmonary veins. Whether these cells are relevant in the genesis of atrial fibrillation requires further study.