Aortic coarctation in pregnancy: outcomes and predictors for cardiovascular and hypertensive complications. Data from the ESC Registry of Pregnancy and Cardiac disease (ROPAC)

Background

Pregnancy in women with repaired aortic coarctation (CoA) has a moderately increased risk (mWHO II-III) of an adverse cardiovascular, obstetric or fetal event, but prospective data to validate this estimated risk is scarce.

Purpose

We examined maternal and fetal outcomes in pregnant women with unrepaired and repaired CoA to identify predictors of adverse outcomes.

Methods

Pregnancies in women with CoA were selected from the worldwide prospective Registry of Pregnancy and Cardiac Disease (ROPAC, n=5739). The frequency and predictors of major adverse cardiac events (MACE, defined as maternal cardiac death, heart failure, atrial fibrillation/flutter, ventricular tachyarrhythmia, endocarditis, thromboembolic events, aortic dissection and acute coronary syndrome), and hypertensive complications (defined as pregnancy-induced hypertension, (pre)eclampsia or HELLP syndrome) were analyzed.

Results

Of 303 pregnancies in women with CoA (median age 30 years, median pregnancy duration 39 weeks), 10% were in women with unrepaired CoA and 27% in women with pre-existing hypertension. There were no maternal deaths. There were 4 neonatal deaths of which 3 occurred after a spontaneous extreme preterm birth. MACE occurred in 4.3% of pregnancies, predominantly involving heart failure (3.3%). MACE rate was similar in unrepaired vs repaired CoA (3.4% vs 4.4%, p=0.814). Predictors of MACE included pre-pregnancy clinical signs of heart failure (OR 31.8, 95% CI 6.8–147.7), LVEF <40% (OR 10.4, 95% CI 1.8–59.5), NYHA class >1 (OR 11.4, 95% CI 3.6–36.3), cardiac medication use (OR 4.9, 95% CI 1.3–18.3) and living in an emerging country (OR 4.88, 95% CI 1.58–15.07). Hypertensive complications occurred in 6.3%, more often in the subgroup with pre-existing hypertension (11% vs 5%, p=0.040). Pre-existing hypertension was the only predictor (OR 2.6, 95% CI 1.01–6.6). Caesarean section was performed in 50% of the total cohort.

Conclusions

Pregnancies in women with CoA are safe, well tolerated and MACE and hypertensive complication rates are low. These findings support mWHO risk score reevaluation to mWHO II for women with CoA without cardiac impairment.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): ESC EURObservational Research Programme (EORP)

Atherosclerotic vascular disease is more prevalent among black ESKD patients on long-term CAPD in South Africa

Background

Occurrence of cardiovascular disease (CVD) in the setting of chronic kidney disease (CKD) can be described as a “cruel alliance”, with CVD responsible for about half of all deaths among CKD patients. Chronic kidney disease patients are more likely to die from CVD than progress to end stage kidney disease (ESKD). Dyslipidaemia, a known traditional risk factor for CVD, is highly prevalent among CKD patients and with an even higher frequency among ESKD patients on dialytic therapies. Prolonged exposure of continuous ambulatory peritoneal dialysis (CAPD) patients to high glucose concentrations in CAPD fluid have been associated with increased risk of cardiovascular events. In this study, we investigated the relationship of atherosclerotic vascular disease (AsVD) to clinical and echocardiographic parameters among black South Africans with CKD (stage 3) and ESKD on CAPD and haemodialysis (HD).

Methods

This was a cross-sectional study of 40 adult (18–65 years) non-diabetic CKD patients (kidney disease outcome quality initiative [KDOQI] stage 3), 40 ESKD patients on CAPD, 40 ESKD patients on HD and 41 age and sex-matched healthy controls. An interviewer-administered questionnaire was used to obtain information on participants’ sociodemographic and cardiovascular risk factors. Anthropometric parameters were measured. Serum blood samples were analysed for creatinine, albumin and lipid profile; lipoprotein ratios, Framingham’s risk score and the 10-year risk of developing coronary heart disease (CHD) were calculated. Echocardiography was performed on all patients and carotid intima media thickness (CIMT) was measured in both right and left carotid arteries at 1 cm proximal to the carotid bulb. Spearman’s rank correlation and binary logistic regression were conducted to determine the relationship of AsVD to clinical and echocardiographic parameters.

Results

Atherosclerotic vascular disease was most prevalent among ESKD patients on CAPD (70%, n = 28/40). Chronic kidney disease and HD patients exhibited a similar prevalence (47.5%, n = 19/40), while the prevalence in controls was 17.1% (n = 7/41). Presence of AsVD was associated with significantly older age, higher waist hip ratio (WHR), left ventricular mass index (LVMI) and Framingham’s 10-year risk of developing CHD. Significant differences in clinical and echocardiographic parameters were observed when the study groups were compared. Age and LVH independently predicted AsVD.

Conclusion

Atherosclerotic vascular disease was more prevalent among CAPD patients compared to pre-dialysis CKD and HD patients. Among all lipoprotein ratios assessed, non-HDL-C showed the most consistent significant difference between the groups. Age (> 40 years) and presence of LVH were independent predictors of AsVD.

Beta-blocker target dosing and tolerability in a dedicated heart failure clinic in Johannesburg

BACKGROUND

Despite the significant clinical benefits of beta-blockers in heart failure with reduced ejection fraction (HFrEF), prescription for and adherence to these agents is reported to be poor. There are few data on the use and tolerance of beta-blocker therapy in patients with HFrEF in South Africa and it is unknown whether these patients would benefit from further heart rate-lowering therapy.

METHODS

Data from all patients with HFrEF attending the heart failure clinic of Charlotte Maxeke Johannesburg Academic Hospital from January 2000 to December 2014 were retrospectively collected. We first determined the rates of beta-blocker intolerance in this population and then categorised the patients according to their most recent dose of beta-blocker (low, moderate or target dose) in order to identify factors associated with beta-blocker intolerance. Lastly, we used the data to identify patients who would be suitable for further treatment with heart rate-lowering therapy.

RESULTS

Five hundred patients, with a median follow up of 58.7 months, were identified during the study period. Black South Africans constituted the majority (66.4%) and most patients had HFrEF due to hypertension (32.8%). At the last recorded clinic visit at the end of the study period, 489 patients (97.8%) were taking a beta-blocker with 59.8% prescribed a beta-blocker at target dose. Consistent with previous data, bradycardia was the commonest cause for failing to reach target beta-blocker dose. Only 61 (12%) patients were on no (n = 11) or low (n = 50) dose of beta-blocker at final clinic visit. As per current guidelines, only 10.6% (n = 53) of this cohort of patients would qualify for further treatment with heart rate-lowering therapy.

CONCLUSIONS

In a dedicated heart failure clinic in South Africa, beta-blockers were well-tolerated in the treatment of HFrEF. The potential role of specific heart rate-lowering therapy in patients treated adequately with heart failure medication and proper up-titration of beta-blockers is relatively small.

Transcriptomic and proteomic changes from medium supplementation and strain evolution in high-yielding Clostridium thermocellum strains

Clostridium thermocellum is a potentially useful organism for the production of lignocellulosic biofuels because of its ability to directly deconstruct cellulose and convert it into ethanol. Previously engineered C. thermocellum strains have achieved higher yields and titers of ethanol. These strains often initially grow more poorly than the wild type. Adaptive laboratory evolution and medium supplementation have been used to improve growth, but the mechanism(s) by which growth improves remain(s) unclear. Here, we studied (1) wild-type C. thermocellum, (2) the slow-growing and high-ethanol-yielding mutant AG553, and (3) the faster-growing evolved mutant AG601, each grown with and without added formate. We used a combination of transcriptomics and proteomics to understand the physiological impact of the metabolic engineering, evolution, and medium supplementation. Medium supplementation with formate improved growth in both AG553 and AG601. Expression of C1 metabolism genes varied with formate addition, supporting the hypothesis that the primary benefit of added formate is the supply of C1 units for biosynthesis. Expression of stress response genes such as those involved in the sporulation cascade was dramatically over-represented in AG553, even after the addition of formate, suggesting that the source of the stress may be other issues such as redox imbalances. The sporulation response is absent in evolved strain AG601, suggesting that sporulation limits the growth of engineered strain AG553. A better understanding of the stress response and mechanisms of improved growth hold promise for informing rational improvement of C. thermocellum for lignocellulosic biofuel production.

Proteinuria, graft outcomes, and cardiovascular risk among kidney transplant recipients in a South African Public Hospital

Proteinuria is a marker of poor long-term graft survival and an independent risk factor for total and cardiovascular mortality in the transplant population. We investigated the prevalence of proteinuria and its relationship with graft function and cardiovascular risk factors in kidney transplant recipients (KTRs). Adult KTRs at the Charlotte Maxeke Johannesburg Academic Hospital were recruited. Patients' records were reviewed for information on their posttransplant follow-up. Echocardiography and carotid Doppler were performed for the assessment of cardiac status and carotid intima-media thickness (CIMT), respectively. Proteinuria was analyzed both as a categorical and continuous variable. Graft dysfunction was defined as estimated glomerular filtration rate of <60 mL/min/1.73 m 2 based on the modification of diet in renal disease formula. Framingham's risk score was used to categorize patients' cardiovascular risk. Inferential and modeling statistics were applied as appropriate using Statistical Package for Social Sciences, and P ≤0.05 was considered statistically significant. One hundred KTRs including 63% males were recruited. Proteinuria was present in 51%, the mean ± standard deviation 24 h urinary protein excretion per day was 1.67 ± 2.0 g/day with a range of 0.4-9.4 g/day. Graft dysfunction was found in 52% of patients and 36% had high cardiovascular disease (CVD) risk. Proteinuric KTRs had high CVD risk, P = 0.002. Proteinuria was associated with graft dysfunction, increased left ventricular mass index, increased CIMT, and anemia. Proteinuria is prevalent; it is a marker of graft dysfunction and is associated with markers of atherosclerosis.

Replicates, Read Numbers, and Other Important Experimental Design Considerations for Microbial RNA-seq Identified Using Bacillus thuringiensis Datasets

RNA-seq is being used increasingly for gene expression studies and it is revolutionizing the fields of genomics and transcriptomics. However, the field of RNA-seq analysis is still evolving. Therefore, we specifically designed this study to contain large numbers of reads and four biological replicates per condition so we could alter these parameters and assess their impact on differential expression results. Bacillus thuringiensis strains ATCC10792 and CT43 were grown in two Luria broth medium lots on four dates and transcriptomics data were generated using one lane of sequence output from an Illumina HiSeq2000 instrument for each of the 32 samples, which were then analyzed using DESeq2. Genome coverages across samples ranged from 87 to 465X with medium lots and culture dates identified as major variation sources. Significantly differentially expressed genes (5% FDR, two-fold change) were detected for cultures grown using different medium lots and between different dates. The highly differentially expressed iron acquisition and metabolism genes, were a likely consequence of differing amounts of iron in the two media lots. Indeed, in this study RNA-seq was a tool for predictive biology since we hypothesized and confirmed the two LB medium lots had different iron contents (~two-fold difference). This study shows that the noise in data can be controlled and minimized with appropriate experimental design and by having the appropriate number of replicates and reads for the system being studied. We outline parameters for an efficient and cost effective microbial transcriptomics study.

Obesity and graft dysfunction among kidney transplant recipients: Increased risk for atherosclerosis

Weight gain after kidney transplant is common, and may be related to graft dysfunction and high cardiovascular risk. We investigated the prevalence of obesity and evaluated the relationship between obesity and graft dysfunction in kidney transplant recipients (KTRs). All patients who received kidney transplant at the Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) between January 2005 and December 2009 were recruited. Information on demographics, clinical characteristics and post-transplant care were documented. All patients underwent transthoracic echocardiography and carotid Doppler ultrasound for the assessment of cardiac status and carotid intima-media thickness (cIMT), respectively. Inferential and modelling statistics were applied. One hundred KTRs were recruited, of which 63 were males. The mean age was 42.2 ± 12.42 years with a range of 19-70 years. The mean body mass index and waist circumference of the recipients were 26.4 ± 4.81 kg/m² and 90.73 ± 14.76 cm, respectively. Twenty-nine patients (29%) were obese; of these, 24 (82.8%) had moderate obesity, 4 (13.8%) had severe obesity, and 1 (3.4%) had morbid obesity. Graft dysfunction was present in 52%. Obese patients were older (P < 0.0001), had graft dysfunction (P = 0.03), higher mean arterial blood pressure (P = 0.022), total cholesterol (P = 0.019), triglycerides (P < 0.0001), left ventricular mass index (P = 0.035) and cIMT (P = 0.036). Logistic regression showed obesity to be independently associated with graft dysfunction (P = 0.033). Obesity after kidney transplantation is common and is associated with graft dysfunction and markers of atherosclerosis.

TYPES OF ALBINISM IN THE BLACK SOUTHERN AFRICA POPULATION

BACKGROUND

Oculocutaneous albinism (OCA) is the most common inherited disorder in Southern African blacks and several types have been described. Molecular techniques, where available, can be used to confirm a clinical diagnosis and the type of OCA, if necessary, and for prenatal diagnosis.

OBJECTIVES

To investigate and classify the different types of albinism commonly found and to determine the clinical implications for each type.

DESIGN

A descriptive survey.

SETTING

Gauteng province, South Africa, and Lesotho.

SUBJECTS

Three groups of subjects with OCA (96 from a genetics clinic, 62 from a dermatology clinic, and 31 from community surveys) from the black African population participated.

MAIN OUTCOME MEASURES

Subjects underwent clinical and/or dermatological examinations and were then classified according to type of OCA.

RESULTS

Four forms of OCA were identified: most (82%) subjects had OCA2 (a tyrosinase- positive type) with three sub-types: those without large freckles (ephelides) on exposed areas (named OCA 2a in this study), those with such freckles (named OCA 2b), and those with brown albinism (BOCA); the remainder had red/rufous albinism, ROCA (OCA 3). The four forms could be distinguished from each other clinically without using molecular genetic testing.

CONCLUSION

The most common types of albinism found in the black population of Southern Africa are OCA2 and OCA3. Given the high prevalence of the disorder, together with the high risk of skin cancer, and the recent persecution of affected individuals in certain East African countries, these findings and their clinical implications have significance in terms of both education and awareness for health professionals and lay people caring for those with albinism.

Evaluation of the melanocortin-1-receptor gene in melanoma predisposition, progression, and recurrence

9018

Background: The melanocortin-1-receptor (MC1R) gene is highly polymorphic in humans. Multiple studies have shown the association between MC1R allelic variants and increased risk of melanoma. Over seventy MC1R single nucleotide polymorphisms (SNPs) have been identified making MC1R a likely target for the development of genetic markers for melanoma predisposition and progression. Alleles described as R and r result in a protein with reduced function compared to wild type, with r alleles having the greatest effect. We sought to investigate the impact of MC1R genotype on risk of developing melanoma and will test for association with disease progression and recurrence in a cohort of melanoma patients enrolled in a prospective study. Methods: Our cohort includes 291 newly diagnosed melanoma patients seen at the New York University Langone Medical Center. The control cohort included 449 subjects. DNA was isolated from leukocytes and analyzed for MC1R SNP status by PCR and direct sequencing. Associations were tested for R-variant R151C and r-variants V60L and V92M. Fisher's Exact test was used to detect significant differences in allele frequency. Odds ratios and confidence intervals were computed for each SNP. Results: Allele frequencies were significantly different in cases and controls for each of the variants (p<0.01). The greatest effect was seen with V60L (Odds Ratio=6.281 95% Confidence Interval 1.77- 22.20). Conclusions: Variants that result in reduced MC1R function increase an individual's risk of developing melanoma. We will continue to test associations with additional variants and determine if these alleles also contribute to risk of disease progression and recurrence. In addition, these variants will be tested for utility as biomarkers for risk assessment of melanoma in a clinical setting.

No significant financial relationships to disclose.

Developing genetic markers for melanoma risk assessment

9046

Background: Risk assessment for melanoma is currently based on phenotype, family and exposure history. This approach is subject to recall bias and excludes at-risk groups such as those with darker skin pigmentation. Poorly stratified risk pools also result in unnecessary dermatologist visits and biopsies for those at lower risk. Use of genetic markers may improve risk assessment; however few susceptibility markers have been developed to date. There have been a number of reports of association between melanoma and genetic markers though few have been replicated or validated. In addition, these studies frequently utilized specific coding region variants as markers and failed to test the entire gene. We have therefore assembled a case-control cohort in which to search for potential biomarkers for melanoma risk by interrogating genes using recently developed tools for genetic analysis. A pilot study was performed to test the utility of our cohort. Methods: A cohort of 326 individuals diagnosed with melanoma and treated at the New York University Langone Medical Center and 400 controls obtained from the New York Cancer project was assembled. Candidate genes were selected based on involvement in determining melanoma predisposition factors (skin pigmentation and DNA repair capability) and previous studies showing association. Three genes, ERCC1, ERCC4 (DNA repair) and MATP (skin pigmentation) were selected. Tag Single Nucleotide Polymorphisms (tSNPs) were selected using Haploview (Hapmap.org) and DNA genotyped (Sequenom Inc, San Diego, CA). Odds ratios and confidence intervals were computed for each SNP. Results: An association was found between SNP rs11615 at the ERCC1 locus and melanoma (Odds ratio = 1.718, 95% Confidence interval: 1.259 - 2.343 for TT vs TC/CC). Conclusions: A tSNP approach is thus useful in identifying associations in our melanoma case-control cohort. Sequence variation at the ERCC1 locus contributes to melanoma risk and the gene will now be screened for clinically useful susceptibility biomarkers. Additional DNA repair and pigmentation genes will also be interrogated using this approach. Genes found to be associated with melanoma will be screened by high- density SNP analysis to identify the most appropriate biomarker/s for use in risk assessment.

No significant financial relationships to disclose.

Mechanism of tyrosinase inhibition by deoxyArbutin and its second-generation derivatives

BACKGROUND

Disorders, such as age spots, melasma and hyperpigmentation at sites of actinic damage, emanate from the augmentation of an increased amount of epidermal melanin.

OBJECTIVES

The ineptness of current therapies in treating these conditions, as well as high cytotoxicity, mutagenicity, poor skin penetration and low stability of skin-depigmenting formulations led us to investigate new compounds that meet the medical requirements for depigmentation agents. We have shown previously that the tyrosinase inhibitor deoxyArbutin (dA) is a more effective and less toxic skin lightener than hydroquinone (HQ).

METHODS

The efficacy and reversibility of dA and its derivatives on inhibiting tyrosine hydroxylase and DOPAoxidase was assessed using standard assays.

RESULTS

dA and its second-generation derivatives inhibit tyrosine hydroxylase and DOPAoxidase activities of tyrosinase dose dependently thereby inhibiting melanin synthesis in intact melanocytes, when used at concentrations that retain 95% cell viability in culture. This depigmenting effect was completely reversible when the compounds were removed. Tyrosinase inhibition was also observed in vitro when tested using human and purified mushroom tyrosinase, establishing that they are direct enzyme inhibitors. Lineweaver-Burk reciprocal plot analysis using mushroom tyrosinase illustrated that dA and its derivatives are more robust competitive inhibitors than HQ, when tyrosine is used as substrate.

CONCLUSIONS

Thus, dA and its second-generation derivatives, which inhibit melanogenesis at safe concentrations by specifically acting on the tyrosinase enzyme at a post-translational level, are promising agents to ameliorate hyperpigmented lesions or lighten skin.

Children with intellectual disability in rural South Africa: prevalence and associated disability

The objective of the present study was to determine the prevalence of intellectual disability (ID) and its associated disabilities in rural South African children aged 2-9 years. It was undertaken in eight villages in the district of Bushbuckridge, Northern Province, South Africa. A two-phase design was utilized. The first phase involved screening children on a house-to-house basis by interviewing mothers or caregivers using an internationally validated questionnaire for detecting childhood disability in developing countries. The second phase consisted of a paediatric/neurodevelopmental assessment of the children who screened positive. A total of 6692 children were screened; 722 (10.8%) had a paediatric evaluation and 238 children were diagnosed with ID, giving a minimum observed prevalence of 35.6 per 1000 children in this population. The prevalence of severe and mild ID was 0.64 per 1000 and 29.1 per 1000 children, respectively. The male:female ratio of children with ID was 3:2. In the affected children, a congenital aetiology for the ID was determined in 49 subjects (20.6%), an acquired aetiology in 15 (6.3%) and the aetiology was undetermined in 174 children (73.1%). Epilepsy (15.5%) and cerebral palsy (8.4%) were the commonest associated disabilities. The present study represents the first data on the prevalence of ID and associated disabilities in rural South African children. The prevalence of ID was comparable with results from a study performed in one other African country (Zambia) as well as those from other developing countries. The data provide an initial factual insight into ID and its associated disabilities for healthcare, social service and educational policy planners. This study provides a basis for the initiation and development of appropriate and integrated services for the best possible care of individuals affected with these disabilities, and for their possible prevention.

Inverse correlation between pink-eyed dilution protein expression and induction of melanogenesis by bafilomycin A1

The pink-eyed dilution protein (p) plays a pivotal role in the synthesis of eumelanin. In its absence, critical melanosomal proteins fail to traffic to the melanosome. Pink-eyed dilution gene (P) mutations are the most common cause of tyrosinase-positive oculocutaneous albinism worldwide. Thus, reports that bafilomycin A1 was able to induce synthesis of melanin in tyrosinase-positive melanomas led us to test the drug on p-null murine melanocytes. We found that in melanocytes lacking p, bafilomycin A1 was able to induce melanin synthesis. These cells, once transfected with an expression vector encoding an epitope-tagged p transcript, failed to respond to the drug. The increase in melanin synthesis is accompanied by a reduction in tyrosinase protein cleavage and secretion with subsequent accumulation within the melanocyte. Bafilomycin A1 has also been reported to induce pigmentation of normal Caucasian melanocytes. Based on these data we hypothesize that p may serve as a key control point at which ethnic skin color variation is determined.

Mislocalization of melanosomal proteins in melanocytes from mice with oculocutaneous albinism type 2

More than 10% of admissions worldwide to institutions for the visually impaired are due to some form of albinism. The most common form, oculocutaneous albinism type 2, results from mutations at the p locus. The function of the p gene is yet to be determined. It has been shown that melanocytes from p -null mice exhibit an abnormal melanosomal ultrastructure in addition to alterations in activity and localization of tyrosinase, a critical melanogenic enzyme. In light of these observations, we examined tyrosinase trafficking in p -null vs wildtype mouse melanocytes in order to explore p function. Electron microscopy of wildtype melan-a and p -null melan-p1 cells demonstrated accumulation of tyrosinase in 50 nm vesicles throughout the cell in the absence of p, an observation corroborated by an increase in tyrosinase activity in vesicle-enriched fractions from melan-p1 compared to melan-a cells. Misrouting in the absence of p was not limited to tyrosinase; a second melanosomal protein, tyrosinase-related protein 1, also trafficked incorrectly. In melan-p1, mislocalization led to secretion of tyrosinase into the medium. Adding tyrosine to the medium was found to partially correct tyrosinase trafficking and to reduce secretion; the cysteine protease inhibitor E64 also reduced secretion. We propose that p is required by melanocytes for transport of melanosomal proteins. In its absence, tyrosinase accumulates in vesicles and, in cultured melanocytes, is proteolysed and secreted.

In Southern Africa, brown oculocutaneous albinism (BOCA) maps to the OCA2 locus on chromosome 15q: P-gene mutations identified

In southern Africa, brown oculocutaneous albinism (BOCA) is a distinct pigmentation phenotype. In at least two cases, it has occurred in the same families as tyrosinase-positive oculocutaneous albinism (OCA2), suggesting that it may be allelic, despite the fact that this phenotype was attributed to mutations in the TYRP1 gene in an American individual of mixed ancestry. Linkage analysis in five families mapped the BOCA locus to the same region as the OCA2 locus (maximum LOD 3.07; theta=0 using a six-marker haplotype). Mutation analysis of the human homologue of the mouse pink-eyed dilution gene (P), in 10 unrelated individuals with BOCA revealed that 9 had one copy of the 2.7-kb deletion. No other mutations were identified. Additional haplotype studies, based on closely linked markers (telomere to centromere: D15S1048, D15S1019, D15S1533, P-gene 2.7-kb deletion, D15S219, and D15S156) revealed several BOCA-associated P haplotypes. These could be divided into two core haplotypes, suggesting that a limited number of P-gene mutations give rise to this phenotype.

Euthanasia and medically assisted suicide--the case for legalizing physician assisted suicide

Ethical and legal debates over ending life are inescapably emotive, controversial and complex. It is, however, increasingly urgent to resolve the debate over the legalization or continued prohibition of physician assisted suicide for a number of reasons, not least of which is the changing public and professional opinion and the growing concern over what may be actually but quietly and surreptitiously occurring in medical practice. The paper assesses the arguments for and against the legalization of this special case of euthanasia and concludes that with appropriate and well-defined criteria, guidelines, review and reporting requirements, the legalization of physician assisted suicide is not only ethical defensible but practical.

Mutational analysis of the modulation of tyrosinase by tyrosinase-related proteins 1 and 2 in vitro

The albino (tyrosinase, Tyrc), brown (tyrosinase-related protein 1, Tyrp1b) and slaty (tyrosinase-related protein 2, tyrp2slt) loci are all involved in the regulation of melanogenesis. Phenotypes of inbred mice mutant at two or more of these loci are not always explicable by simple summation of the established or suspected catalytic functions of the gene products. These phenotypes suggest that relationships among the proteins extend beyond the obvious fact that they catalyze different steps in the same melanogenic pathway, and that they may also interact intimately in such a way that a mutation in one impacts the function of the other(s). Previous studies have attributed catalytic activities to each member of this trio; however, it has been difficult to study the proteins individually, either in vivo or in tissues or cells. Therefore, we undertook to transfect the genes, in revealing combinations, into COS-7 cells (which have no melanogenic apparatus of their own) to clarify the interacting functions of their encoded proteins. Specifically, we attempted to evaluate the effects of Tyrp1 and Tyrp2 proteins on tyrosinase protein. We report evidence that Tyrp1 stabilizes tyrosinase, confirming previous observations, and, in addition, demonstrate that Tyrp1 decreases tyrosinase activity. By contrast, Tyrp2 increases tyrosinase activity by stabilizing the protein. We conclude that both Tyrp1 and Tyrp2, in addition to other catalytic functions they may possess, act together to modulate tyrosinase activity.

The Quattro valve and active infective endocarditis of the mitral valve

BACKGROUND AND AIM OF THE STUDY

Even today, infective endocarditis remains a therapeutic challenge. Active endocarditis at the time of valve implantation is an important risk factor for the development of prosthetic valve infection. This study reports results following implantation of the Quattro valve, a stentless chordally supported quadrileaflet mitral valve made from bovine pericardium.

METHODS

The Quattro valve was implanted in seven patients (four females, three males; mean age 34 years) requiring isolated mitral valve replacement for active bacterial endocarditis. All had congestive heart failure; two were in cardiogenic shock. The diagnosis of active endocarditis was based on clinical and echocardiographic findings, together with macroscopic evidence of acute infection at surgery, blood culture or histopathological evidence of valve infection. Postoperatively, all patients received at least four weeks of parenteral antibiotic therapy.

RESULTS

Congestive heart failure (and large pedunculated vegetations and mobile septic left atrial thrombi in two patients) prompted early surgical intervention. Patients underwent surgery at a mean of 7 days (range: 1-16 days) after admission. Endocarditis was caused by Gram-positive cocci in all patients except one. At a mean follow up of 15 months (range: 6-24 months) all patients were alive and symptomatically improved. To date, all remain free of prosthetic valve endocarditis, reoperation and thromboembolism.

CONCLUSION

The Quattro valve can be implanted safely in patients with acute bacterial endocarditis. The results also reflect the benefit of early surgical intervention in patients with infective endocarditis complicated by congestive heart failure, with or without large vegetations.

Transoesophageal echocardiographic demonstration of mechanism for right-to-left shunting across a patent foramen ovale in acquired tricuspid regurgitation

This case report describes a patient who presented with left middle cerebral artery infarction and was found to have a systolic right-to-left shunt across a patent foramen ovale. These features were secondary to severe acquired tricuspid regurgitation.

Epilepsy in rural South African children--prevalence, associated disability and management

OBJECTIVE

To determine the prevalence of epilepsy and its associated disabilities in rural South African children aged 2-9 years.

SETTING

Eight villages in the district of Bushbuckridge, Northern Province, South Africa.

DESIGN

A two-phase design was used. The first phase involved screening children on a house-to-house basis by interviewing mothers or caregivers using an internationally validated questionnaire for detecting childhood disability in developing countries. The second phase consisted of a paediatric/neurodevelopmental assessment of the children who screened positive.

RESULTS

A total of 6,692 children were screened; 722 (10.8%) had a paediatric evaluation and 49 (0.73%) had epilepsy. The lifetime and active prevalences of epilepsy in these children were 7.3/1,000 and 6.7/1,000 respectively. Associated developmental disability was recorded in 35 affected children (71.4%), including 8 (16.3%) in whom this was moderate to severe. More than a half of the children with epilepsy (57.1%) did not receive anticonvulsant medication.

CONCLUSION

The prevalence of epilepsy in the rural childhood population investigated is higher than that recorded in most similar studies from sub-Saharan Africa, and the poor utilisation of appropriate anticonvulsant treatment is cause for concern. This study highlights the paucity of relevant information on the epidemiology of epilepsy in South Africa and that the system available for its management, especially in rural areas, appears to have functional deficiencies. Appropriate research is needed to identify the problems in service delivery and to enable the planning and implementation of an appropriate primary health care-based system for the diagnosis and management of epilepsy in children.

Identification of P gene mutations in individuals with oculocutaneous albinism in sub-Saharan Africa

Oculocutaneous albinism (OCA) is an inherited disorder resulting in hypopigmentation of the skin, hair, and eyes. OCA type 2 (tyrosinase-positive) is the most common recessively inherited disorder among southern African Blacks. OCA2 is also seen in southern African Caucasoids, but is less frequent. The gene responsible for this type of albinism, P, is the human homolog of the mouse pink-eyed dilution gene. Mutations at this locus are also responsible for the milder hypopigmentation phenotype seen in individuals with brown oculocutaneous albinism (BOCA). A common African P mutation was identified in Black OCA2 individuals, and has since been shown to occur in Black individuals with brown OCA as well. This mutation is a 2.7 kb interstitial deletion. In this study, we undertook to screen the coding region of the P gene for mutations in the non-2.7 kb deletion alleles of OCA2 patients who did not carry the deletion allele in either one or both of their P genes. We identified four mutations (A334V, 614delA, 683insG [corrected], 727insG) in a group of 39 unrelated Black OCA2 patients with a total of 52 non-2.7 kb deletion OCA2 genes. When taking all OCA2 cases into consideration, including those homozygous for the 2.7 kb deletion mutation, these account for a further 1.7% of OCA2 mutations in southern African Blacks, increasing the overall mutation detection rate to 78.7%. Three mutations (E678K, L688F, I370T) were identified in a group of 15 Black patients with an initially unclassified type of OCA and another three mutations (IVS 14-2 (a-->g), V350M, P743L) were identified in nine Caucasoid OCA patients. Relatively few mutations, all with low frequency, were identified in the non-2.7 kb deletion OCA genes. We propose that other mutations may lie either within intronic sequence or within the promoter region of the gene.

Economic case for the integration of chiropractic services into the health care system

The role and position of chiropractic care in the health care system must be transformed from being alternative and separate to alternative and mainstream. This transformation requires that chiropractic services become integrated in the many health care delivery organizations that collectively constitute the health care system. There is solid and impressive economic and related justification for the desired integration. Chiropractic care is a cost-effective alternative to the management of neuromusculoskeletal conditions by other professions. It is also safer and increasingly accepted by the public, as reflected in the growing use and high patient retention rates. There is much and repeated evidence that patients prefer chiropractic care over other forms of care for the more common musculoskeletal conditions. The public interest will be well served by this transformation. Musculoskeletal disorders and injuries are the second and third most costly categories of health problems in economic burden-of-illness studies. They rank first as a cause in the prevalence of chronic health problems and long-term disability and rank at the top for activity limitations and short-term disability. They rank first as a reason for consultation with a health professional and second as a reason for the use of prescription and nonprescription drugs. These conditions are more prevalent among the poor, lower-middle income groups, and the elderly, yet those are precisely the groups that make the least use of chiropractic care for reasons of inadequate insurance coverage. The integration of chiropractic care into the health care system should serve to reduce health care costs, improve accessibility to needed care, and improve health outcomes.

The quadrileaflet mitral valve: follow-up in rheumatic heart disease

This prospective study evaluated the clinical performance of a novel stentless quadrileaflet bovine pericardial mitral valve implanted at one center since December 1996. After giving informed consent, patients were included in the study if they required isolated mitral valve replacement. All underwent comprehensive clinical evaluation, as well as transthoracic M-mode, two-dimensional and Doppler (pulsed, continuous, and color) echocardiography preoperatively and postoperatively at 1 month, 3 months, and annually thereafter. Mitral valve area was derived by planimetry, the pressure half-time method, and the continuity equation. The degree of mitral regurgitation was semi-quantitated using color Doppler. In all 38 patients with rheumatic valvular heart disease (mean age 35+/-13 years) were monitored for 13.8+/-7.5 months (range, 1 to 29 months). All but three patients are alive and symptomatically improved (functional New York Heart Association class I or II). One valve was explanted because of early prosthetic valve endocarditis. There were no episodes of thromboembolism or anticoagulation-related hemorrhage. Left ventricular function was maintained with increased cardiac output and low transmitral pressure gradients. The mitral valve area was larger when measured by pressure half-time and planimetry than by the continuity equation (P<.05). In an independent clinical evaluation of a subset of 30 patients, mitral stenosis was considered absent in 33%, mild in 30%, mild to moderate in 26%, and moderate in 10% of cases. No or less than or equal to mild mitral regurgitation was noted in the majority of patients postoperatively, both clinically and echocardiographically. We are encouraged by the clinical performance of the quadrileaflet mitral valve and with patient outcome. Long-term follow-up data are needed to assess durability.

Exercise-induced hyperkalemia and concentration of Na,K-pumps in skeletal muscle in mitral stenosis: effect of balloon mitral valvotomy

BACKGROUND AND AIMS OF THE STUDY

The study aim was to examine the effects of balloon mitral valvotomy (BMV) on exercise-induced hyperkalemia, and on changes in the concentration of Na,K-pumps in skeletal muscle, as an exaggerated exercise-induced rise in potassium concentration ([K+]) may contribute to exertional fatigue and breathlessness.

METHODS

Eight subjects were evaluated with mitral stenosis (mean age 34 +/- 5.2 years) before, and at two weeks and four months after BMV. Subjects underwent incremental exercise to exhaustion for exercise-induced rise in [K+] and vastus lateralis biopsy for concentration of Na,K-pumps.

RESULTS

Mean (+/- SE) valve area increased from 0.89 +/- 0.03 cm2 before to 1.75 +/- 0.05 cm2 after BMV. There was a progressive increase in VO2,max (15.3 +/- 1.6, 17.2 +/- 1.4 and 19.9 +/- 1.9 l/kg/min) at baseline, early after and later after BMV, respectively (p < 0.01). The rise in [K+] with absolute workload fell progressively at early and late follow up post-BMV (p < 0.05), but was unchanged when plotted against percentage of VO2,max to match for relative workload. The concentration of Na,K-pumps was similar to baseline at early follow up (233 +/- 10 versus 228 +/- 15 pmol/g wet weight), but was significantly increased at late follow up after four months (265 +/- 17 pmol/g; p < 0.05). When the relationship between the concentration of Na,K-pumps and the exercise-induced rise in [K+] was studied, a negative correlation was found. However, correlation analysis for the effects of changes in Na,K-pumps on changes in exercise hyperkalemia after BMV was not significant.

CONCLUSIONS

The progressive reduction in exercise-induced rise in [K+] after BMV may contribute to the progressive improvement in exercise performance. The increased concentration of Na,K-pumps in skeletal muscle may assist in this improvement, and emphasizes the importance of peripheral adaptations in clinical improvement after BMV.

Avoiding fundamental reform: current cost containment strategies in Canada

Provincial governments in Canada are trying very hard to contain and possibly reduce health care expenditure. The wide ranging effort and frequent announcements of yet another cost cutting measure, including deinsurance, stand in marked contrast to the complacency of earlier periods. This activist and serious effort to reform the system is certainly welcome, yet the reforms are not adequate and ignore some fundamental and structural problems of Canada's health care system. Health care reform must do one or more of three things, i.e., improve efficiency, effectiveness, and/or equity of the system. Many cost-cutting measures in Canada achieve none of these objectives and merely postpone costs to a later time or shift the burden on to the sick. Fundamental health reforms include the incentive systems influencing physician behavior and choices; efficiency gains via manpower substitution; more effective control over the supply and distribution of medical manpower; and changes in the organization and design of health care delivery systems. But these fundamental reforms are not being pursued in Canada even though this is an opportune time for such reforms. Also discussed is the potential for and problems associated with managed and/or public sector competition. This article is essentially a critical review of current cost containment efforts in Canada.

The stentless quadrileaflet bovine pericardial mitral valve: echocardiographic assessment

BACKGROUND AND AIMS OF THE STUDY

Recently, a stentless chordally supported quadrileaflet mitral valve (QMV) bioprosthesis made of selected tanned bovine pericardium treated to minimize calcification, has become available for clinical trial. The aim of this study was to report both the echocardiographic appearance and hemodynamic performance of this valve by means of echocardiography.

METHODS

The QMV was implanted in 22 patients (mean age 38 +/- 12 years) requiring isolated mitral valve replacement for valve lesions not deemed suitable for repair. Echocardiography was performed pre-operatively, and at one and three months postoperatively. Transthoracic echocardiography (TTE) was used to monitor mean instantaneous pressure gradient as calculated from the long modified Bernoulli equation, cardiac index (CI), pressure half-time and effective orifice area (EOA) using the Hatle and continuity equations. Regurgitation patterns were sought by color Doppler transesophageal echocardiography in all valves intraoperatively following valve implantation, and by TTE in the outpatient clinic at follow up.

RESULTS

After a mean follow up of 8.3 months (range: 1 to 18 months), all patients were well and symptomatically improved. At three months postoperatively, the mean pressure gradient ranged from 1.7 to 2.2 mmHg. The EOA was larger using the Hatle as compared with the continuity equation (2.4 +/- 0.7 cm2 versus 1.8 +/- 0.5 cm2, respectively; p < 0.005). Mitral regurgitation was trivial in 77% and mild in 14% of patients at 3 months after surgery; moderate mitral stenosis was noted in one patient. The CI improved significantly postoperatively (p < 0.005), and left ventricular function was maintained.

CONCLUSIONS

The hemodynamic performance of this novel prosthesis is favorable. Although follow up is too short to assess durability, it is hoped that the unique design and improved valve preservation technique of this device will enhance long-term durability.

The stentless quadrileaflet bovine pericardial mitral valve: early clinical results

BACKGROUND AND AIMS OF THE STUDY

Although bioprosthetic valves currently in use have low thrombogenicity, durability remains very unsatisfactory. Valve failure occurs early from calcification, and later from tissue wear. Stentless design lessens the latter, and anticalcification treatments the former. Recently, a stentless chordally supported quadrileaflet mitral valve (QMV) bioprosthesis made of selected tanned bovine pericardium, treated to minimize calcification, has become available for clinical study. The aim of this study was to report the early results relating to valve performance, and patient outcome.

METHODS

Since December 1996, the QMV has been implanted in 23 patients (mean age 38 +/- 12 years) requiring isolated mitral valve replacement for valve lesions not suited for repair. All patients were symptomatic (three in NYHA functional class II, 16 in class III, four in class IV). Preoperatively, all underwent full clinical and echocardiographic assessment, and intraoperative transesophageal evaluation immediately after valve implantation. Blood tests for hemolysis were performed preoperatively and at 3 months after surgery.

RESULTS

After a mean follow up of 8.3 months (range: 1 to 18 months), 22 patients were alive and symptomatically improved (NYHA class I or II). One patient died of sternal sepsis soon after surgery. There have been no reoperations, nor cases of infective endocarditis or thromboembolism. Subclinical hemolysis was shown pre- and postoperatively in 35% and 32% of cases, respectively. Intraoperative transesophageal echocardiography post valve implantation demonstrated mitral regurgitation which was trivial in 15 patients (78%) and mild in five (22%).

CONCLUSIONS

The QMV can be implanted safely, and the early clinical results relating to patient outcome and valve performance are encouraging.

A benefit-cost analysis of two-dose measles immunization in Canada

In 1992, because of the limitations of the one-dose measles immunization program, the National Advisory Committee on Immunization (NACI) recommended a two-dose measles immunization program to eliminate measles. More recently, NACI recommended also a special catch-up program to prevent predicted measles outbreaks and to achieve an earlier elimination of measles. The objective of this study was to complete a benefit-cost analysis of a two-dose immunization program with and without a mass catch-up compaign compared with the current one-dose program. The resulting benefit: cost ratios vary between 2.61:1 and 4.31:1 depending on the strategy used and the age of the children targeted. Given the parameters established for this analysis, the benefits of a second-dose vaccination program against measles far outweight the costs of such a program under all scenarios.

The role of consumers in health care decision making

This paper focuses on the results of a survey of chief executive officers and consumer board members of Ontario hospitals and community health centres regarding the role of consumers in health care decision making. The opinions of both the chief executive officer and consumer board member respondents were elicited regarding the value of consumer input in decision making for the organizations studied. Results indicate that consumer board members feel that their input into organizational decision making is valued, chief executive officers value the input of consumers, and consumer involvement in decision making is increasing. More women are now involved on boards of the organizations studied, but visible minority representation remains low on hospital boards. Consumer board members feel that their decision making is influenced by providers on the board.

Rufous oculocutaneous albinism in southern African Blacks is caused by mutations in the TYRP1 gene

Oculocutaneous albinism (OCA) is the most common autosomal recessive disorder among southern African Blacks. There are three forms that account for almost all OCA types in this region. Tyrosinase-positive OCA (OCA2), which is the most common, affects approximately 1/3,900 newborns and has a carrier frequency of approximately 1/33. It is caused by mutations in the P gene on chromosome 15. Brown OCA (BOCA) and rufous OCA (ROCA) account for the majority of the remaining phenotypes. The prevalence of BOCA is unknown, but for ROCA it is approximately 1/8,500. Linkage analysis performed on nine ROCA families showed that ROCA was linked to an intragenic marker at the TYRP1 locus (maximum LOD score = 3.80 at straight theta=.00). Mutation analysis of 19 unrelated ROCA individuals revealed a nonsense mutation at codon 166 (S166X) in 17 (45%) of 38 ROCA chromosomes, and a second mutation (368delA) was found in an additional 19 (50%) of 38 chromosomes; mutations were not identified in the remaining 2 ROCA chromosomes. In one family, two siblings with a phenotypically unclassified form of albinism were found to be compound heterozygotes for mutations (S166X/368delA) at the TYRP1 locus and were heterozygous for a common 2.7-kb deletion in the P gene. These findings have highlighted the influence of genetic background on phenotype, in which the genotype at one locus can be influenced by the genotype at a second locus, leading to a modified phenotype. ROCA, which in southern African Blacks is caused by mutations in the TYRP1 gene, therefore should be referred to as "OCA3," since this is the third locus that has been shown to cause an OCA phenotype in humans.

Feasibility of prenatal diagnosis and carrier detection in South African haemophilia A patients

The feasibility of DNA diagnosis for haemophilia A was tested in South African patients and families by screening for the common inversion mutation in the factor VIII gene and for the intragenic microsatellite markers in introns 13 and 22. The allele frequencies at the two microsatellite loci were significantly different, with informativity being higher in the Negroid (100%) than the Caucasoid group (67%). In severely affected haemophiliacs the inversion was found in 43% (6/14) of Negroids but in only 32% (13/41) of Caucasoids. Presence of a second common unidentified mutation may account for the low frequency in the latter. Haplotype analysis shows a disproportionately high frequency of an (AC)20 intron 13-(AC)26 intron 22 inversion negative Caucasoid haemophilia chromosome, supporting a founder effect.

Exercise capacity and skeletal muscle structure and function before and after balloon mitral valvuloplasty

This study evaluated the effects of balloon mitral valvuloplasty (BMV) on exercise capacity and skeletal muscle structure and function in 10 subjects with mitral stenosis (mean age +/- SD 33 +/- 5.5). Measurements were obtained before, and 2 weeks and 4 months after BMV to provide baseline data, to examine the effects of improved hemodynamics, and to examine the effects of resumption of normal physical activity, respectively. Valvuloplasty caused an increase in mitral valve area (0.89 +/- 0.04 to 1.75 +/- 0.07 cm2; mean +/- SE), and an increase in resting cardiac output (3.8 +/- 0.18 to 4.6 +/- 0.19 L/min, p < 0.05). At early follow-up after 2 weeks, subjects did more work (31% increase, p < 0.01) and had greater maximal oxygen consumption (11% increase, p < 0.01). However, measurements reflecting skeletal muscle histology, biochemistry, and function were unaltered at this stage. Four months after BMV, subjects had a further increase in exercise capacity compared with both baseline (58% increase, p < 0.01) and early follow-up (20% increase, p < 0.05). There were associated late increases compared with baseline in quadriceps cross-sectional area (66 +/- 5.8 vs 61 +/- 5.5 cm2, p < 0.05) and torque production (125 +/- 14 vs 118 +/- 16 Nm, p < 0.05). The percentage of slow twitch type I fibers increased compared with baseline (41 +/- 2.0% vs 33 +/- 3.1%, p < 0.05), as did the size of type II fibers (5.9 +/- 0.49 vs 4.9 +/- 0.57 microns2 x 10(3), p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Interventional cardiology in South Africa

South Africa is a country in political and cultural flux. Because of the iniquitous system of apartheid, inequalities have been perpetuated at all levels including health care. Due to the high prevalence of ischemic heart disease and rheumatic heart disease, coronary angiography, PTCA, intracoronary stenting, and balloon valvuloplasty have become established cardiological procedures in South Africa. However, a new political dispensation promises changes to health care, which will impact on interventional cardiology. With a proposed emphasis on primary health care, resources for tertiary health care will probably be curtailed. Thus consideration will have to be given to reducing expenditure by careful review of indications for expensive interventional procedures and developing new ideas to contain costs. This will be the challenge facing cardiologists in a "New South Africa".

The tyrosinase-positive oculocutaneous albinism gene shows locus homogeneity on chromosome 15q11-q13 and evidence of multiple mutations in southern African negroids

Tyrosinase-positive oculocutaneous albinism (ty-pos OCA) is an autosomal recessive disorder of the melanin pigmentary system. South African ty-pos OCA individuals occur with two distinct phenotypes, with or without darkly pigmented patches (ephelides, or dendritic freckles) on exposed areas of the skin. These phenotypes are concordant within families, suggesting that there may be more than one mutation at the ty-pos OCA locus. Linkage studies carried out in 41 families have shown linkage between markers in the Prader-Willi/Angelman syndrome (PWS/AS) region on chromosome 15q11-q13 and ty-pos OCA. Analysis showed no obligatory crossovers between the alleles at the D15S12 locus and ty-pos OCA, suggesting that the D15S12 locus is very close to or part of the disease locus, which is postulated to be the human homologue, P, of the mouse pink-eyed dilution gene, p. Unlike caucasoid "ty-pos OCA" individuals, negroid ty-pos OCA individuals do not show any evidence of locus heterogeneity. Studies of allelic association between the polymorphic alleles detected at the D15S12 locus and ephelus status suggest that there was a single major mutation giving rise to ty-pos OCA without ephelides. There may, however, be two major mutations causing ty-pos OCA with ephelides, one associated with D15S12 allele 1 and the other associated with D15S12 allele 2. The two loci, GABRA5 and D15S24, flanking D15S12, are both hypervariable, and many different haplotypes were observed with the alleles at the three loci on both ty-pos OCA-associated chromosomes and "normal" chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative results of percutaneous balloon mitral valvuloplasty using the Trefoil/Bifoil and Inoue balloon techniques

This study compared the results in 150 consecutive patients with rheumatic mitral stenosis who underwent percutaneous balloon mitral valvuloplasty by means of a Trefoil/Bifoil balloon catheter (n = 100, Group 1) or the Inoue balloon catheter (n = 50, Group 2). There was significant improvement in mitral valve area after valvuloplasty in both groups: in Group 1 mitral valve area improved from 0.92 +/- 0.22 to 2.14 +/- 0.64 cm2 (P < 0.001) and in Group 2 from 1.0 +/- 0.26 to 2.06 +/- 0.59 cm2 (P < 0.001). There was no significant difference in the mitral valve area, mean diastolic gradient or mean left atrial pressure between Group 1 and Group 2 patients after valvuloplasty. There was a higher complication rate in Group 1 patients but this was largely related to our early learning experience with the procedure. The Trefoil/Bifoil catheter technique is more complex and involved a longer screening time: Group 1 (39 +/- 15 min) vs. Group 2 (22 +/- 10 min); P < 0.001. The cost of the Inoue balloon technique, however, was almost twice that of the Trefoil/Bifoil technique. This may have important implications for developing countries with limited health care budgets and a high prevalence of rheumatic heart disease.

Mitral valve area calculations immediately after percutaneous balloon mitral valvuloplasty: effect of the atrial septal defect

OBJECTIVES

The aim of this study was to assess the effect of the atrial septal defect on mitral valve area calculations after balloon mitral valvuloplasty.

BACKGROUND

There is poor correlation between the hemodynamic-derived and Doppler mitral valve area immediately after mitral valvuloplasty. The reasons for this are unclear.

METHODS

Twenty-five patients with severe mitral stenosis were studied. After balloon mitral valvuloplasty, serial mitral valve area calculations were performed with 1) the mitral dilating catheter across the atrial septum, 2) the 7F catheter across the atrial septum, and 3) with the atrial puncture site occluded with the balloon catheter.

RESULTS

The mitral valve area determined by the Gorlin formula with balloon occlusion of the atrial septum was smaller than the mitral valve area determined without balloon occlusion (mean +/- SD 1.8 +/- 0.43 vs. 2.24 +/- 0.67 cm2, p < 0.005 for the mitral dilating catheter across the atrial septum and 1.8 +/- 0.43 vs. 2.19 +/- 0.52, p < 0.05 for the 7F catheter across the atrial septum). The mean of the differences between the mitral valve area derived by the Gorlin formula and by the Doppler pressure half-time method was smaller with the atrial septum occluded than when the dilating catheter or the 7F catheter was across the atrial septum (0.12 +/- 0.26 vs. 0.56 +/- 0.48 cm2 [p < 0.005] and 0.12 +/- 0.26 vs. 0.48 +/- 0.55 cm2 [p < 0.05]). Left to right shunting was detected less frequently by oximetry (60%), than by shunt ratios calculated by using the cardiac output measurements with and without balloon occlusion of the atrial septum (84%).

CONCLUSIONS

The presence of left to right shunts after mitral valvuloplasty may account for some of the discrepancies between mitral valve area found at cardiac catheterization and that by the Doppler pressure half-time method; thus, the latter method may be reliably used to follow up patients in the long term.