Search PubMed⌕ Search

Biomedical subjects

N Sreeram

Publications and source records attributed to N Sreeram.

At least 37 records · Page 2Linked to original sources
PubMed2001

Congenital heart block: development of late-onset cardiomyopathy, a previously underappreciated sequela.

OBJECTIVE: We report 16 infants with complete congenital heart block (CHB) who developed late-onset dilated cardiomyopathy despite early institution of cardiac pacing. BACKGROUND: Isolated CHB has an excellent prognosis following pacemaker implantation. Most early deaths result from delayed initiation of pacing therapy or hemodynamic abnormalities associated with congenital heart defects. METHODS: A multi-institutional study was performed to identify common clinical features and possible risk factors associated with late-onset dilated cardiomyopathy in patients born with congenital CHB. RESULTS: Congenital heart block was diagnosed in utero in 12 patients and at birth in four patients. Ten of 16 patients had serologic findings consistent with neonatal lupus syndrome (NLS). A pericardial effusion was evident on fetal ultrasound in six patients. In utero determination of left ventricular (LV) function was normal in all. Following birth, one infant exhibited a rash consistent with NLS and two had elevated hepatic transaminases and transient thrombocytopenia. In the early postnatal period, LV function was normal in 15 patients (shortening fraction [SF] = 34 +/- 7%) and was decreased in one (SF = 20%). A cardiac pacemaker was implanted during the first two weeks of life in 15 patients and at seven months in one patient. Left ventricular function significantly decreased during follow-up (14 days to 9.3 years, SF = 9% +/- 5%). Twelve of 16 patients developed congestive heart failure before age 24 months. Myocardial biopsy revealed hypertrophy in 11 patients, interstitial fibrosis in 11 patients, and myocyte degeneration in two patients. Clinical status during follow-up was guarded: four patients died from congestive heart failure; seven required cardiac transplantation; one was awaiting cardiac transplantation; and four exhibited recovery of SF (31 +/- 2%). CONCLUSIONS: Despite early institution of cardiac pacing, some infants with CHB develop LV cardiomyopathy. Patients with CHB require close follow-up not only of their cardiac rate and rhythm, but also ventricular function.

Cardiomyopathy, Dilated↗
PubMed2001

Catheter ablation of incisional atrial tachycardia using a novel mapping system: LocaLisa.

Incisional atrial tachycardia occurs due to reentry around surgical scars. Pharmacological therapy is often ineffective. This study assessed the efficacy of a novel mapping system (LocaLisa) in facilitating catheter ablation of incisional atrial tachycardia circuits. Eight consecutive patients (four men, four women) with incisional atrial tachycardia (median age 23.5 years, range 9-44) following previous repair of congenital heart defects underwent transcatheter mapping and ablation of the arrhythmogenic substrate using a mapping system (LocaLisa) that allows localization of endocardial electrodes in a three-dimensional space. Critical isthmuses for the tachycardia circuits were identified by demonstrating concealed entrainment using standard pacing and mapping techniques. Scars and natural anatomic barriers were marked on the LocaLisa image. Lines of block were created by radiofrequency current application between scars and natural anatomic barriers, or between two scars, to close isthmuses demonstrated to be critical for the reentrant circuit. All lines of block were verified in both directions. All reentrant circuits around incisions were successfully ablated. Seven additional tachycardia mechanisms were identified in four patients (common atrial flutter [n = 4], atrioventricular nodal [AVN] reentry [n = 2], ectopic atrial tachycardia [n = 1]) and were also ablated in a single session. The mean fluoroscopy time was 28.4 +/- 13.8 minutes. All patients are arrhythmia-free at a median follow-up of 20 (6-22) months. The LocaLisa mapping system is effective for identification of scars and ablation targets, for confirming lines of block, and facilitating ablation of complex reentrant circuits.

Adult↗
PubMed2000

[Balloon angioplasty as the primary treatment for coarctation of the aorta in 30 children; immediate results and follow-up].

OBJECTIVE: Evaluation of the results of balloon dilatation in coarctation of the aorta in children. DESIGN: Retrospective. METHOD: In the years 1990-1999 30 patients with a congenital coarctation of the aorta were treated with balloon angioplasty in the Children's Heart Centre of Utrecht University Medical Centre, the Netherlands. The group comprised 5 girls and 25 boys, with a mean age of 4.8 years (range 1 month-16 years) without severe associated congenital heart defects or a long segment coarctation. Follow-up included Doppler echocardiography and MRI within the first 6 years after the procedure. The fall of the pressure gradient was assessed with Student's t-test for paired observations and the reintervention period was calculated by the Kaplan-Meier method. RESULTS: No children died. Of 30 procedures performed, 28 (93%) were considered successful. Mean pressure gradient was reduced from 36.2 mmHg (SD: 12.7) to 13.1 mmHg (SD: 9.3) (p < 0.001). Mean follow-up was 4.1 years; the follow-up of 11 patients was longer than 5 years. Four patients (13%) developed a recoarctation. No aneurysm formation was encountered (n = 14). CONCLUSION: Balloon angioplasty for the treatment of native coarctation of the aorta in children may be an efficient and not very damaging solution for this selected group of patients.

Adolescent↗
PubMed2000

Radiofrequency thermal balloon angioplasty in an experimental model of peripheral arterial stenosis.

RATIONALE: To assess the effect of thermal balloon angioplasty on surgically created peripheral arterial stenoses. METHODS: Unilateral femoral arterial stenoses were created in 17 neonatal lambs (Dorset X Suffolk/Mule), using absorbable sutures. Six to 8 weeks later, the stenoses were dilated using either a standard (N=5), or thermal balloon angioplasty (N=9). Immediate angiography, flow and pressure gradient measurements were made to assess the acute result following either procedure. The survivors were followed up for a further period of 4 to 6 weeks, and a terminal angiographic study performed. The thermally treated segments of vessels were removed for qualitative histologic analysis. RESULTS: Thermal angioplasty appeared to be acutely successful in eight of nine animals, compared with one of five successful procedures following standard angioplasty. Higher therapeutic temperatures (> or = 80 degrees C) were associated with vascular complications. At the terminal study, stenoses had recurred in four of six survivors successfully treated with thermal angioplasty. Histologic studies demonstrated non-uniform effects of thermal dilation on the vessel wall, with variable changes ranging from partial or full-thickness tears, fibroblastic or myocyte proliferation, and disorganization of the vessel wall layers. CONCLUSION: Thermal angioplasty appears to be acutely more beneficial compared with standard angioplasty. However there is a significant recurrence of stenoses, and non-uniform changes in the vessel wall.

Angioplasty, Balloon↗
PubMed2000

Exchange of pacing or defibrillator leads following laser sheath extraction of non-functional leads in patients with ipsilateral obstructed venous access.

Occlusion of the subclavian or brachiocephalic vein in pacemaker or defibrillator patients prohibits ipsilateral implantation of new leads with standard techniques in the event of lead malfunction. Three patients are presented in whom laser sheath extraction of a non-functional lead was performed in order to recanalise the occluded vein and to secure a route for implantation of new leads. This technique avoids abandoning a useful subpectoral site for pacing or defibrillator therapy. The laser sheath does not affect normally functioning leads at the same site.

Adult↗
PubMed1999

[Implantable ECG recorder revealed the diagnosis in a baby with apparent life-threatening events].

A 14-month-old boy went through episodes of cyanosis and brief loss of consciousness. Extensive investigations failed to lead to a diagnosis, until an implanted ECG recorder revealed ECG abnormalities suggestive of strangulation. Interviews with the father and mother showed that this was indeed the case. The diagnosis of 'Münchhausen by proxy' was made. Psychiatric assistance and home help were called in. The child recovered well. If there is a suspicion of arrhythmia as the cause of apparent life-threatening events, prolonged ECG recordings are necessary. In a clinical environment it is possible to make continuous ECG recordings during a limited period. An insertable recorder allows continuous ECG recordings during a syncopal event and can be used for prolonged monitoring. The patient presented is the youngest infant in the world in whom such a device has been implanted.

Arrhythmias, Cardiac↗
PubMed1999

Homozygous premature truncation of the HERG protein : the human HERG knockout.

Background-In long-QT syndrome (LQTS), heterozygosity for a mutation in 1 of the K(+) channel genes leads to prolongation of the cardiac action potential, because the aberrant protein exhibits "loss of function." HERG, which is involved in LQT2, is the gene encoding the rapid component of the delayed rectifier, I(Kr). Methods and Results-In a consanguineous family, a stillbirth was followed by the premature birth of a child in distress due to ventricular arrhythmia in the presence of QT prolongation. LQTS was diagnosed, beta-blocker therapy was begun, and a pacemaker was implanted. She developed well and remained symptom-free for 1.5 years. In the index patient, we identified a duplication of bp 558 to 600 in exon 4 of HERG on both alleles. This will result in a frameshift and a premature stop codon before the S1 domain of the HERG protein. Because it is present on both alleles, no functional I(Kr) is anticipated. The same mutation was found heterozygously in both parents and homozygously in the stillborn brother. Conclusions-It is concluded that absence of I(Kr) gives rise to a severe cardiac phenotype, with no indication of malfunction of any other organ.

Cation Transport Proteins↗
PubMed1999

Competitive pulmonary flow in infancy: the effect of respiration.

Superior caval flow during positive pressure mechanical ventilation and spontaneous breathing was investigated by Doppler echocardiography in a neonate with a coexisting superior cavopulmonary shunt and an aortopulmonary shunt. During positive pressure ventilation, retrograde systolic flow in the superior vena cava was recorded, with low velocity anterograde flow. This pattern was reversed during spontaneous respiration. Low intrathoracic pressure plays an important role in maintaining anterograde pulmonary blood flow in patients with this physiology.

Arteriovenous Shunt, Surgical↗
PubMed1999

Sustained high pressure double balloon angioplasty of calcified conduits.

OBJECTIVE: To assess the efficacy of prolonged high pressure angioplasty for dilatation of calcified and stenotic cardiac conduits in children. DESIGN: A prospective study of consecutive patients presenting with calcified and stenotic conduits. SETTING: Two tertiary paediatric cardiology departments. METHODS: Sustained (up to five minutes), high pressure (up to 18 atmospheres), double balloon angioplasty was performed in six calcified and stenotic cardiac conduits (five consecutive patients, three male, two female, age 4 to 17 years). Four patients had right ventricle to pulmonary artery (RV-PA) conduits, and one had two venous conduits in a Fontan circulation. RESULTS: Marked reductions in right ventricle to pulmonary artery gradients, from a median (range) of 48 (40 to 62) mm Hg to 11 (5 to 16) mm Hg, and in right ventricle to femoral artery pressure ratios, from a median of 0.8 (0.72 to 0.86) to 0.4 (0.33 to 0.44), were achieved for all RV-PA conduits. All five patients had sustained clinical improvement at follow up (median follow up 12 months) and none has required reintervention or surgery. CONCLUSIONS: Prolonged high pressure double balloon angioplasty may have a role in prolonging the interval between conduit replacements in a subset of patients with complex heart defects.

Adolescent↗
PubMed1999

Lung perfusion studies after detachable coil occlusion of persistent arterial duct.

OBJECTIVE: To evaluate relative lung perfusion following complete occlusion of persistent arterial duct with detachable Cook coils. METHODS: Ductal occlusion using detachable coils was performed in 35 patients (median age 3.9 years, range 0.5 to 16; 32 native ducts, three patients with previous devices). If the duct could be crossed with a 0.035 inch guidewire and a 4 F catheter after coil implantation, a further coil was implanted. Between one and seven coils were used (median two). RESULTS: Complete ductal occlusion was confirmed by echocardiography 24 hours after the procedure in all patients. Lung perfusion scans were performed three months after the procedure in 33 of 35 patients (two older patients with a single coil each did not attend). Decreased perfusion to the left lung (defined as < 40% of total lung flow) was observed in only one patient, who had previously had a 17 mm Rashkind umbrella implanted. There was no correlation between left lung perfusion and peak left pulmonary artery Doppler velocities (r = 0.27 and p = 0.125 for the entire group; r = 0.29 and p = 0.124 after excluding patients with previous devices). CONCLUSIONS: Coil occlusion is effective in achieving complete closure of the duct. An aggressive approach using multiple coils did not compromise perfusion to the left lung.

Adolescent↗
PubMed1998

Double chambered right ventricle: delineation by multiplane transoesophageal echocardiography.

Three consecutive patients (median age 5 years; median weight 15 kg) with double chambered right ventricle (DCRV) were studied by multiplane transoesophageal echocardiography (TOE), using a specially designed paediatric probe. Using a 30 degrees angulation from the longitudinal plane, the body and outflow tract of the right ventricle could be imaged with minimal foreshortening, allowing detailed description of the level and nature of obstruction. In all cases, angiography and subsequent surgical inspection confirmed the TOE findings. Multiplane TOE should avoid the necessity for angiography in the preoperative assessment of this unusual lesion.

Cardiac Catheterization↗
PubMed1998

Catastrophic transcatheter baffle fenestration for failing Fontan physiology.

Transcatheter fenestration and balloon dilation of an atrial baffle created from native atrial tissue was attempted in a 15-year-old girl with failing Fontan physiology and protein-losing enteropathy. After transseptal puncture, initial dilations with a 10-mm and 12-mm diameter balloon resulted in an inadequate fenestration, with no significant decrease of right atrial pressure or systemic arterial saturation. Dilation of the fenestration with a 16-mm-diameter balloon produced a tear of the atrial septum and subsequent death. Balloon dilation of native atrial tissue may result in uncontrolled tears of the atrial septum.

Abnormalities, Multiple↗