Mid-term study of transcatheter aortic valve implantation in an Asian population with severe aortic stenosis: two-year Valve Academic Research Consortium-2 outcomes

INTRODUCTION

Transcatheter aortic valve implantation (TAVI) is an effective treatment for high-risk or inoperative patients with severe aortic stenosis. Given the unique characteristics of Asian populations, questions regarding mid-term outcomes in Asians undergoing TAVI have yet to be addressed. We evaluated the two-year clinical outcomes of TAVI in an Asian population using Valve Academic Research Consortium-2 definitions.

METHODS

This prospective study recruited 59 patients from a major academic medical centre in Singapore. The main outcomes were two-year survival rates, peri-procedural complications, symptom improvement, valvular function and assessment of learning curve.

RESULTS

Mean age was 76.8 years (61.0% male), mean body surface area 1.6 m² and mean logistic EuroSCORE 18.7%. Survival was 93.2%, 86.0% and 79.1% at 30 days, one year and two years, respectively. At 30 days post TAVI, the rate of stroke was 1.7%, life-threatening bleeding 5.1%, acute kidney injury 25.0%, major vascular complication 5.1%, and new permanent pacemaker implantation 6.8%. 29.3% of TAVI patients were rehospitalised (47.1% cardiovascular-related) within one year. These composite outcomes were measured: device success (93.2%); early safety (79.7%); clinical efficacy (66.1%); and time-related valve safety (84.7%). Univariate analysis found these predictors of two-year all-cause mortality: logistic EuroSCORE (hazard ratio [HR] 1.07; p < 0.001); baseline estimated glomerular filtration rate (HR 0.97; p = 0.048); and acute kidney injury (HR 5.33; p = 0.022). Multivariate analysis identified non-transfemoral TAVI as a predictor of cardiovascular-related two-year mortality (HR 14.64; p = 0.008).

CONCLUSION

Despite the unique clinical differences in Asian populations, this registry demonstrated favourable mid-term clinical and safety outcomes in Asians undergoing TAVI.

Statins for Primary Prevention of Cardiovascular Disease in Elderly Patients: Systematic Review and Meta-Analysis

BACKGROUND

Statins have been shown to be beneficial in primary and secondary prevention settings; however, their role in the elderly remains a clinical conundrum, given that age-related factors could alter the risk-benefit ratio of statin treatment. This study aimed to critically evaluate the efficacy and safety of statins for primary prevention of cardiovascular disease (CVD) in the elderly.

METHODS

We systematically reviewed randomized controlled trials comparing any statins with placebo or usual care for primary prevention of CVD in subjects aged ≥65 years. Relative risks (RRs) using a random effects model were calculated and sensitivity analyses were performed to assess the robustness of findings.

RESULTS

Eight studies (n = 25,952) were included in the meta-analysis. Statins significantly reduced the risks of composite major adverse cardiovascular events (RR 0.82, 95% CI 0.74-0.92), nonfatal myocardial infarction [MI] (0.75, 0.59-0.94) and total MI (0.74, 0.61-0.90). Treatment effects of statins were statistically insignificant in fatal MI (0.43, 0.09-2.01), stroke (fatal: 0.76, 0.24-2.45; nonfatal: 0.76, 0.53-1.11; total: 0.85, 0.68-1.06) and all-cause mortality (0.96, 0.88-1.04). Significant differences were not observed in myalgia (0.88, 0.69-1.13), elevation of hepatic transaminases (0.98, 0.71-1.34), new-onset diabetes (1.07, 0.77-1.48), serious adverse events (1.00, 0.97-1.04) and discontinuation due to adverse events (1.10, 0.85-1.42). The occurrence of myopathy, rhabdomyolysis and cognitive impairment was largely unreported in the included trials.

CONCLUSIONS

From a risk-benefit perspective, there is a role of statins for the primary prevention of major adverse cardiovascular events in elderly patients. Further studies are needed to ascertain the benefits of statins on fatal MI, stroke and all-cause mortality.

Refractory hypoxaemia following inferior ST-segment elevation myocardial infarction: case report of an unusual complication and review of treatment strategies

Right ventricular (RV) infarction is not an uncommon complication of acute left ventricular infarction. It has been established that RV dysfunction post myocardial infarction (MI) is associated with increased mortality and morbidity. When RV infarction occurs in a patient with previously dormant patent foramen ovale (PFO), an unusual presentation of persistent refractory hypoxaemia ensues. We present a case of new RV infarction in a patient with underlying ischaemic cardiomyopathy, which was complicated by acute right-to-left shunting through the PFO. He was treated with percutaneous coronary intervention (PCI) and subsequent percutaneous PFO closure. We will also review the existing literature with regards to diagnostic and management strategies for patients with this unusual sequelae of MI.

Demographics of severe valvular aortic stenosis in Singapore

INTRODUCTION

The treatment of aortic valve stenosis (AS) is seeing renewed interest mainly due to the availability of transcatheter therapies. However, the number of epidemiological studies of this disease in Singapore is limited. We aimed to describe the aetiology and clinical presentation of AS in Singapore, as well as patients' attitudes toward it. Our findings may facilitate the future planning and utilisation of resources to better manage these patients.

METHODS

249 consecutive patients who underwent transthoracic echocardiography (from April 1999 to April 2008) and diagnosed with severe AS were assessed. Demographic and clinical data were collected, and patients' decisions on surgery were determined.

RESULTS

The mean patient age was 71 (range 23-98) years. 50.2% of patients were male. The commonest presenting symptom was dyspnoea, and 40 (16.0%) patients had coexistent atrial fibrillation. The aetiology of AS was degenerative in 216 (86.7%), rheumatic in 11 (4.4%) and related to a bicuspid valve in 22 (8.9%) patients. The average peak velocity across the aortic valve was 4.2 ± 0.8 m/s and the mean aortic valve area was 0.76 ± 0.13 cm2. The overall mean logistic EuroSCORE was 10.7 ± 12.3. 105 (42.2%) patients who were offered surgery refused. 87 (35%) deaths were seen during the follow-up period (mean duration 14.5 months), which also saw 68 (27%) patients undergo surgery and 86 (34%) patients hospitalised for heart failure.

CONCLUSION

Degenerative AS was the commonest aetiology in this contemporary cohort of patients. Despite the known benefits of surgery, the refusal rate for surgery remained high.

Transcatheter aortic valve implantation: implications for Asian patients

BACKGROUND

transcatheter aortic valve implantation is now an accepted therapy for patients with severe aortic valve stenosis who are deemed inoperable, and it is a reasonable alternative for patients with high surgical risk. This study assessed the clinical outcomes of this procedure and the implications of transcatheter aortic valve implantation for such patients.

METHODS

14 consecutive patients with severe aortic valve stenosis, who underwent transcatheter aortic valve implantation, were assessed. Baseline clinical characteristics, procedural information, and clinical outcomes and complications were compared at baseline and at follow-up. Thirty-day mortality was also assessed.

RESULTS

the mean age of the patients was 81 ± 8 years (35% females). The mean Society of Thoracic Surgeons score was 6.8 ± 3.7. Most patients had chronic kidney disease with an estimated glomerular filtration rate of 44.5 ± 14.9 mL·kg(-1)·min(-1). The mean annulus diameter was 21.9 ± 1.7 mm, and 8 (57%) patients received 23-mm valves. After transcatheter aortic valve implantation, the mean transaortic gradient and aortic valve area improved from 42.9 ± 19.4 to 8.9 ± 3.1 mm Hg (p < 0.001) and 0.7 ± 0.1 to 1.5 ± 0.3 cm(2) (p < 0.001), respectively. The 30-day mortality for this cohort was 7%.

CONCLUSION

transcatheter aortic valve implantation can be performed successfully in carefully selected Asian patients. The decision to undertake this procedure should be guided by the surgical team.

Relation between combining evidence-based medications on mortality following myocardial infarction in patients with and without renal impairment

BACKGROUND

Antiplatelet agents, beta-blockers, statins and ACE inhibitors have been shown to reduce mortality in patients following myocardial infarction (MI). However, it is uncertain if the combination of these agents has a similar impact on mortality following MI in patients with renal dysfunction.

METHODS

We studied 5529 consecutive patients with confirmed MI between January 2000 and December 2003. Data on baseline demographics, co-morbidities and in-hospital management were collected prospectively. Glomerular filtration rate (GFR) was estimated using the 4-component Modification of Diet in Renal Disease equation. Based on discharge use of evidence-based medications, the patients were divided into those using 0, 1, 2, 3 or 4 medications. The impact of medication use on 1-year mortality was then assessed for patients with GFR > or =60 ml/min/1.73 m2 (group I) and GFR < 60 ml/min/1.73 m2 (group 2).

RESULTS

Mean age was 63 +/- 13 years with 71% men.The prevalence of reduced GFR was 35% and the adjusted odds ratio for I-year mortality of patients in group 2 compared to those in group I was 1.86 (95% CI 1.54-2.25, P < 0.001). Compared with patients with no medication, the adjusted odds ratio for 1-year mortality was lower in patients with 1, 2, 3 and 4 medications in both groups. There was no significant interaction between the number of medications used and GFR.

CONCLUSION

Increased use of combined evidence-based medications was independently associated with a lower 1-year post MI mortality. Such therapies offer similar survival benefit in patients with and without renal dysfunction.

Impact of left ventricular diastolic dysfunction on left atrial volume and function: a volumetric analysis

AIMS

Diastolic dysfunction may result in elevation of left ventricular (LV) and atrial pressures, resulting in left atrial (LA) remodelling. We examined the effects of LV diastolic dysfunction on LA volume and function.

METHODS AND RESULTS

We measured LA volume and function in 83 patients with normal LV systolic function. The LV diastolic function grade was defined using traditional Doppler measures of diastolic function. LA volumes were measured using the ellipsoid method. Maximum LA volume (Vol(max)) was indexed to the body surface area(.) The passive filling, conduit and active emptying volumes were estimated and corrected for indexed LA Vol(max). Indexed LA Vol(max) was strongly associated with LV diastolic function grade (Spearman P < 0.01, r(s) = 0.79). An indexed LA Vol(max) > 19.7 mL/m(2) predicted diastolic dysfunction with 97% sensitivity and 96% specificity. Compared with normal controls, corrected passive filling and conduit volumes were lower, and corrected active emptying volume was higher in patients with Grade I diastolic dysfunction (0.38 vs. 0.51, P = 0.02; 1.65 vs. 3.29, P < 0.001; 0.59 vs. 0.44, P = 0.001), resulting in a similar corrected total emptying volume (0.97 vs. 0.96, P= ns). Patients with higher grades of diastolic dysfunction, however, had lower corrected passive filling, conduit, active, and total emptying volumes.

CONCLUSION

LA remodelling occurs in patients with LV diastolic dysfunction and LA volume expressed the severity of diastolic dysfunction. Initially, the LA compensates for changes in LV diastolic properties by augmenting active atrial contraction. As the severity of diastolic dysfunction increases, this compensatory mechanism fails as atrial mechanical dysfunction sets in, resulting in lower total atrial emptying volume.

Risk Factor Profile and Treatment Patterns of Patients with Atherothrombosis in Singapore: Insight from the REACH Registry

Introduction: Atherothrombosis is the leading cause of cardiovascular mortality. The Reduction of Atherothrombosis for Continued Health (REACH) Registry provided information on atherosclerosis risk factors and treatment. Singapore was one of the 44 participating countries in the REACH Registry. The objective of this study was to determine the atherosclerosis risk factor profile and treatment patterns in Singapore patients enrolled in the REACH Registry. Materials and Methods: The REACH Registry is an international prospective observational registry of subjects with or at risk for atherothrombosis. Patients aged 45 years or older with established vascular disease [coronary artery disease (CAD), cerebrovascular disease (CVD), peripheral arterial disease (PAD)] or 3 or more atherosclerosis risk factors were recruited between 2003 and 2004. Results: A total of 881 patients (64.4% male) were recruited in Singapore by 63 physicians. The mean age was 64 ± 9.8 years (range, 45 to 95). Seven hundred and one (79.6%) patients were symptomatic (CAD 430, CVD 321, PAD 72) while 180 (20.4%) patients had ≥3 risk factors. Approximately 13% of symptomatic patients had symptomatic polyvascular disease. There was a high proportion of diabetes mellitus (57%), hypertension (80.6%) and hypercholesterolemia (80.1%). A substantial proportion of symptomatic patients were current smokers (14.1%). Approximately half of the patients were either overweight or obese [abdominal obesity, 54.3%; body mass index (BMI) 23-27.5, 45.9%; BMI ≥27.5, 23.3%]. Patients were undertreated with antiplatelet agents (71.9% overall; range, 23.9% for ≥3 risk factors to 84.7% for PAD) and statins (76.2% overall; range, 73.6% for PAD to 82.1% for CAD). Risk factors remained suboptimally controlled with a significant proportion of patients with elevated blood pressure (59.4% for ≥3 risk factors and 48.6% for symptomatic patients), elevated cholesterol (40% for ≥3 risk factors and 24.4% for symptomatic patients) and elevated blood glucose (45% for ≥3 risk factors and 19.8% for symptomatic patients). Conclusion: Established atherosclerosis risk factors are common in Singapore patients in the REACH Registry; and obesity is a major problem. Most of these risk factors remained suboptimally controlled. Key words: Obesity, Undertreatment, Vascular disease

Risk factor profile and treatment patterns of patients with atherothrombosis in Singapore: insight from the REACH Registry

INTRODUCTION

Atherothrombosis is the leading cause of cardiovascular mortality. The Reduction of Atherothrombosis for Continued Health (REACH) Registry provided information on atherosclerosis risk factors and treatment. Singapore was one of the 44 participating countries in the REACH Registry. The objective of this study was to determine the atherosclerosis risk factor profile and treatment patterns in Singapore patients enrolled in the REACH Registry.

MATERIALS AND METHODS

The REACH Registry is an international prospective observational registry of subjects with or at risk for atherothrombosis. Patients aged 45 years or older with established vascular disease [coronary artery disease (CAD), cerebrovascular disease (CVD), peripheral arterial disease (PAD)] or 3 or more atherosclerosis risk factors were recruited between 2003 and 2004.

RESULTS

A total of 881 patients (64.4% male) were recruited in Singapore by 63 physicians. The mean age was 64 +/- 9.8 years (range, 45 to 95). Seven hundred and one (79.6%) patients were symptomatic (CAD 430, CVD 321, PAD 72) while 180 (20.4%) patients had > or =3 risk factors. Approximately 13% of symptomatic patients had symptomatic polyvascular disease. There was a high proportion of diabetes mellitus (57%), hypertension (80.6%) and hypercholesterolemia (80.1%). A substantial proportion of symptomatic patients were current smokers (14.1%). Approximately half of the patients were either overweight or obese [abdominal obesity, 54.3%; body mass index (BMI) 23-27.5, 45.9%; BMI > or =27.5, 23.3%]. Patients were undertreated with antiplatelet agents (71.9% overall; range, 23.9% for > or =3 risk factors to 84.7% for PAD) and statins (76.2% overall; range, 73.6% for PAD to 82.1% for CAD). Risk factors remained suboptimally controlled with a significant proportion of patients with elevated blood pressure (59.4% for > or =3 risk factors and 48.6% for symptomatic patients), elevated cholesterol (40% for > or =3 risk factors and 24.4% for symptomatic patients) and elevated blood glucose (45% for > or =3 risk factors and 19.8% for symptomatic patients).

CONCLUSION

Established atherosclerosis risk factors are common in Singapore patients in the REACH Registry; and obesity is a major problem. Most of these risk factors remained suboptimally controlled.

Cor triatriatum presenting in adulthood: A case report

Cor triatriatum is a rare congenital defect in which a fibromuscular membrane divides the left atrium into two distinct chambers. We described a case of cor triatriatum with interesting Doppler flow signal in a 39-year-old female. The diagnosis was confirmed on cardiac catheterization and surgery.

Stroke-Work Loss Underestimates Hemodynamic Significance of Aortic Stenosis in Patients with Hypertension

BACKGROUND

Stroke-work loss (SWL) represents the amount of energy the left ventricle dissipates as heat because of outflow obstruction. Recent studies suggest that SWL > 25% was the most clinically efficient Doppler measure for predicting hemodynamic significance, symptomatic status, and outcome in patients with aortic stenosis (AS). However, SWL may be affected by systolic blood pressure (SBP).

OBJECTIVE

To determine if SWL reliably predicts hemodynamic significance of AS in patients with hypertension.

METHODS

We studied 42 consecutive patients with hemodynamically significant AS requiring aortic valve replacement (AVR). Data on demographics, preoperative hemodynamics, and echocardiographic parameters were obtained. SWL was measured using the formula SWL = 100 x mean PG/ (mean PG + SBP), where PG is transaortic pressure gradient. Patients were considered hypertensive if their BP > 140/90 mmHg or if they are on antihypertensive medications.

RESULTS

There were 27 males (64%) and mean age was 68 +/- 11 years. Twenty-four patients (57%) were hypertensive. Mean SBP was 134 +/- 24 mmHg, mean transaortic PG 47 +/- 20 mmHg, effective valve orifice area (EOA) by Doppler estimation 0.74 +/- 0.23 cm(2), and SWL 26 +/- 9%. Patients with hypertension had smaller SWL than normotensives (table I). SWL was >25% in 20 (49%) patients, and fewer patients with hypertension have SWL >25% (33% vs 71%, P = 0.019). Of note, patients with SWL < or =25% had significantly higher SBP (145 +/- 21 mmHg vs 122 +/- 22 mmHg, P = 0.02).

CONCLUSION

SWL underestimates the hemodynamic significance of aortic stenosis in the majority of patients with hypertension.

'Office-hour' ambulatory blood pressure monitoring is sufficient for blood pressure diagnosis

We conducted this study to determine whether 'office hour', defined as time period from 0800 to 1800 hours, ambulatory blood pressure monitoring (ABPM) predicts daytime ('waking-hour') and 24-h ABPM results, and to examine the impact of sleep disturbance on ABPM and nocturnal dip. Eighty-four patients (mean age 49+/-18 years, 47 males) were studied. Systolic, diastolic and mean 4-, 6-, 8-, 'office-hour' as well as 'waking-hour' blood pressures (BPs) were obtained from 24-h ABPM readings. Of these, no statistical differences were found between 8-h and 'office-hour' systolic, diastolic and mean BPs compared to 'waking-hour' values. There was complete concordance between 'office-hour' and 'waking-hour' ABPM diagnosis based on British Hypertension Society definitions. Sleep disturbance was found in 22 patients (26%). Although nocturnal dip was not significantly different in either sleep-disturbed or non-disturbed patients, patients who reported sleep disturbance had significantly higher proportion of borderline/abnormal BP diagnosis compared to non-sleep-disturbed counterpart during both 'waking hour' and night time. In patients without sleep disturbance, there was complete concordance between 'office-hour', 'waking-hour' and 24-h ABPM diagnosis based on British Hypertension Society definitions. 'Office-hour' ABPM is predictive of 'waking-hour' and 24-h ambulatory BP readings. Sleep disturbance is common in patients undergoing the test, and significantly raises the BP readings. We therefore propose 'office-hour' ABPM as an accurate, reliable and comfortable method of continual non-invasive BP monitoring, and omitting routine night time BP monitoring.

Coronary hemodynamics in patients with symptomatic hypertrophic cardiomyopathy

The purpose of this study was to analyze coronary hemodynamics and determine a possible mechanism for microvascular dysfunction in patients with symptomatic hypertrophic cardiomyopathy (HC). Although patients with HC have been shown to have microvascular dysfunction and reduced coronary flow reserve (CFR), the mechanism by which this occurs is not well understood. We studied coronary hemodynamics in 8 patients with symptomatic HC and compared them with 8 matched controls. Compared with controls, patients with HC had higher coronary blood flow, lower coronary resistance, and lower CFR. Patients with HC also had abnormal phasic coronary flow characteristics. These results suggest that the reduction of CFR in patients with HC may be secondary to near maximal vasodilation of the microcirculation in the basal state.

High-sensitivity C-reactive protein is predictive of medium-term cardiac outcome in high-risk Asian patients presenting with chest pain syndrome without myocardial infarction

INTRODUCTION

High-sensitivity C-reactive protein (hs-CRP) has been shown to be predictive of cardiac events but data among Asians is comparatively few. We evaluated the role of hs-CRP in the prediction of adverse cardiac outcome in a cohort of high-risk patients presenting with chest pain syndrome without myocardial infarction (MI).

MATERIALS AND METHODS

Three hundred and forty-seven patients were prospectively recruited over an 18-month period and patients with MI as documented by serial electrocardiogram abnormalities, and creatinine kinase or troponin elevation were excluded. Mean follow-up duration was 901 +/- 306 days. Kaplan-Meier and Cox proportional hazards modelling were used to evaluate outcome and determine association with predictor variables.

RESULTS

The composite primary endpoint of cardiac mortality, non-fatal MI, cardiac failure or coronary revascularisation procedure (coronary artery bypass grafting or angioplasty) unrelated to the index admission was reached in 37 patients. History of previous MI (P = 0.002), presence of at least 1 coronary artery with > or =50% stenosis (P = 0.028) and elevated hs-CRP levels were associated with an adverse cardiac outcome (P = 0.001 for CRP in the upper quartile, and 0.002 for CRP > or = 1mg/L, respectively). None of the traditional cardiovascular risk factors (hypertension, diabetes mellitus, dyslipidaemia, significant family history, smoking, male gender and increased age) was predictive. Multivariate modelling showed elevated hs-CRP to confer the highest risk for an adverse cardiac outcome (P <0.001).

CONCLUSION

Hs-CRP is useful in further stratifying high-risk multi-ethnic patients presenting with chest pain despite no evidence of MI. Close follow-up and aggressive management of these patients may be warranted.

The impact of diabetes mellitus on the prognostic value of a normal dobutamine stress echocardiogram in patients with intermediate to high cardiovascular risk

INTRODUCTION

There is currently limited data on the prognostic value of a normal dobutamine stress echocardiogram (DSE) in patients with intermediate to high cardiovascular risk. The impact of diabetes mellitus, recently recognised as a cardiovascular risk-equivalent, has not been previously evaluated. This study aims to determine the prognostic value of a normal DSE in these patients.

METHODS

The study population includes all patients with two cardiovascular risk factors or diabetes mellitus and a normal DSE (baseline and peak stress) with three months follow-up. A total of 122 patients (47 females, 75 males; mean age 59.6 years) were recruited. Impact of diabetes mellitus on subsequent cardiovascular events was determined.

RESULTS

Diabetes mellitus was present in 32.8 percent, hypertension in 72.1 percent, smoking in 27.0 percent, family history of premature coronary artery disease in 15.6 percent, and hypercholesterolemia in 66.4 percent. On follow-up until 6.4 years (mean 4.1 years), there were four myocardial infarctions (0.8 percent per patient/year) and five revascularisation procedures (1.0 percent per patient/year). The majority of adverse events occurred among patients with diabetes mellitus (three out of four myocardial infarctions; four out of five revascularisations). Diabetes mellitus independently predicted subsequent cardiac events on both univariate and multivariate analyses (p value is equal to 0.015 and 0.011, respectively). Presence of diabetes mellitus also conferred a worse outcome on survival analysis (p value is equivalent to 0.0046).

CONCLUSION

The presence of diabetes mellitus adversely affects clinical outcome despite a normal DSE. Patients without diabetes mellitus, but with intermediate to high cardiovascular risk, and a normal DSE have a better medium term outcome.

V(D)J rearrangement in Nijmegen breakage syndrome

Repair of DNA double-strand breaks is essential for maintenance of genomic stability, and is specifically required for rearrangement of immunoglobulin (Ig) and T cell receptor (TCR) loci during development of the immune system. Abnormalities in these repair processes also contribute to oncogenic chromosomal rearrangements that underlie many lymphoid malignancies. Nijmegen breakage syndrome (NBS) is a rare autosomal recessive condition characterized by immunodeficiency, radiation sensitivity, and increased predisposition to lymphoid cancers bearing oncogenic Ig and TCR locus translocations. NBS patients fail to produce nibrin, a protein required for the nuclear localization and function of a DNA repair complex that includes Mre11 and Rad50. Mre11 has biochemical properties that suggest a potential role in V(D)J recombination. We studied V(D)J recombination in NBS cells in vitro and in vivo, using cell lines and peripheral blood leukocyte DNA from NBS patients. We found that NBS cells were competent to rejoin signal substrates with normal efficiency and high fidelity. Coding substrates were similarly rejoined efficiently, and coding end structures appeared normal. In B cells from NBS patients, the spectrums of IgH CDR3 regions were diverse and normally distributed. Moreover, the lengths and composition of Igkappa VJ joins and IgH VDJ joins derived from NBS and normal subjects were indistinguishable. Our data indicate that nibrin plays no essential role in V(D)J recombination and is not required for the generation of an apparently diverse B cell repertoire.

Identification, characterization, and mapping of a mouse homolog of the gene mutated in Nijmegen breakage syndrome

The rare autosomal recessive disorder Nijmegen breakage syndrome (NBS) results from mutations in the NBS1 gene on human chromosome 8q21. A mouse homolog of the NBS1 gene was isolated and its nucleotide sequence determined. Somatic cell hybrid analysis and fluorescence in situ hybridization were used to map this gene, Nbn, to mouse chromosome band 4A. Northern blotting revealed comparable levels of Nbn transcripts in most tissues in the mouse. However, transcripts were elevated 10-20 fold in the testes, consistent with a possible role for the product of the Nbn gene in meiotic recombination.

Retroviral expression of the NBS1 gene in cultured Nijmegen breakage syndrome cells restores normal radiation sensitivity and nuclear focus formation

The majority of cases of the autosomal recessive disorder Nijmegen breakage syndrome (NBS) are associated with null mutations in the NBS1 gene, which encodes a 95 kDa protein, nibrin. Cell lines established from NBS patients fail to express nibrin and display hypersensitivity to ionizing radiation and dysregulation of the nuclear localization of two key proteins involved in DNA repair, Mre11 and Rad50. Conclusive proof that mutations in the NBS1 gene are responsible for NBS requires that re-expression of normal nibrin in NBS cells complements these phenotypes. In the current study, retroviral expression vectors containing a normal copy of the NBS1 gene or a mutated form derived from a NBS patient were introduced into a well- characterized NBS cell line. Introduction of a normal copy of the NBS1 gene, but not the mutant form, resulted in robust expression of nibrin that displayed correct nuclear localization. Expression of nibrin also restored the ability of nibrin, Mre11 and Rad50 to complex and to redistribute within the nucleus in response to ionizing radiation. Radiation sensitivity of NBS cells expressing wild-type nibrin was restored to normal levels. Hence, introduction of the NBS1 gene can correct the phenotypes observed in NBS cells.

Clinical characteristics and outcome in postinfarction pseudoaneurysm

The clinical characteristics and outcome in 22 patients with postinfarction pseudoaneurysm were studied. The medium-term outcome was poor (median follow-up 3.6 years), but cardiac rupture was uncommon in patients treated conservatively.

Spontaneous aortic laceration causing flail aortic valve and acute aortic regurgitation

Spontaneous laceration of the aorta is an unusual cause of flail aortic valve. We report a case of acute aortic regurgitation caused by flail aortic valve as a result of spontaneous laceration of the ascending aorta. The role of transesophageal echocardiography in the diagnosis of this condition is discussed.

Prognostic value of a Doppler index combining systolic and diastolic performance in idiopathic-dilated cardiomyopathy

This study sought to investigate, in patients with idiopathic-dilated cardiomyopathy, the clinical and prognostic value of a Doppler-derived index of myocardial function that combines systolic and diastolic time intervals of the left heart cycle. The Doppler index was measured in 75 patients (aged 61 +/- 13 years; 45 men and 30 women) in sinus rhythm and 75 age- and sex-matched controls. Ejection time was measured from the left ventricular outflow Doppler signal. The sum of isovolumic times was obtained by subtracting the ejection time from the interval between cessation and onset of mitral inflow measured from the mitral inflow velocity profile. The index was the sum of isovolumic times divided by ejection time. The values of the Doppler index in patients with idiopathic-dilated cardiomyopathy (0.85 +/- 0.32) were significantly higher than values in controls (0.37 +/- 0.08, p < 0.001). During follow-up of 5 years, 1 patient underwent cardiac transplantation and 36 patients died, 29 of cardiac, 5 of noncardiac, and 2 of unknown causes. Univariate analysis demonstrated that the Doppler index (chi-square = 18.3, p < 0.001), ejection fraction (chi-square = 15.2, p <0.001), symptom status (chi-square = 9.2, p = 0.002), and mitral deceleration time (chi-square = 5.2, p = 0.02) were significant predictors of outcome. However, multivariate stepwise analysis of these variables showed that the Doppler index (chi-square = 10.7, p = 0.001) and ejection fraction (chi-square = 6.7, p = 0.01) were the most significant independent predictors of outcome. The Doppler index reflects disease severity and has incremental prognostic value in dilated cardiomyopathy. Ease of use, nongeometric dependency, excellent separation of clinical groups, and a strong relation to outcome enhance its appeal.

Mechanisms of hemolysis after mitral valve repair: assessment by serial echocardiography

OBJECTIVES

We sought to determine, using serial echocardiography, the hydrodynamic mechanisms involved in the occurrence of hemolysis after mitral valve repair.

BACKGROUND

Recently, fluid dynamic simulation models have identified distinct patterns of mitral regurgitant flow disturbances in patients with mitral prosthetic hemolysis that were associated with high shear stress and may therefore produce clinical hemolysis. Rapid acceleration, fragmentation, and collision jets were associated with high shear stress and hemolysis whereas slow deceleration and free jets were not.

METHODS

We reviewed serial echocardiographic studies of 13 consecutive patients with hemolytic anemia after mitral valve repair who were referred for mitral reoperation between January 1985 and December 1996 (group 1). Thirteen patients undergoing reoperation for mitral regurgitation after mitral valve repair but without hemolysis served as controls (group 2).

RESULTS

The mitral regurgitant jet was central in origin in 12 group 1 patients and 9 group 2 patients (Fisher exact test, p= 0.3). The other patients had para-ring regurgitation. Group 1 patients had collision (n=11), rapid acceleration (n=2) or fragmentation (n=1) jets whereas group 2 patients had slow deceleration (n=11) or free jets (n=2) (Fisher exact test, p < 0.0001). One patient with hemolysis had both collision and rapid acceleration jets. The "culprit" jet could be identified on the postbypass transesophageal echocardiography (TEE) study in only 1 patient at the time of initial mitral repair. Twelve group 1 patients underwent reoperation, with subsequent resolution of hemolysis in all patients. At reoperation, the initial repair was found to be intact in 8 (67%) patients.

CONCLUSION

Distinct patterns of flow disturbance associated with high shear stress were identified by color Doppler imaging in patients with hemolysis after mitral valve repair. The majority (92%) of these color flow disturbances were not present during intraoperative postbypass TEE study after initial mitral repair and subsequently developed in the early postoperative period.

Value of a Doppler-derived index combining systolic and diastolic time intervals in predicting outcome in primary pulmonary hypertension

Primary pulmonary hypertension is characterized by elevated pulmonary arterial pressure and vascular resistance, frequently producing right heart failure and death. Therefore, the Doppler right ventricular (RV) index, which is a measure of global RV function, could be a useful predictor of outcome in primary pulmonary hypertension. The Doppler RV index, defined as the sum of isovolumic contraction time and isovolumic relaxation time divided by ejection time, was retrospectively measured in 53 patients (38 women, aged 45 +/- 14 years) with primary pulmonary hypertension. Ejection time was measured from the pulmonary outflow velocity signal. The sum of isovolumic contraction time and isovolumic relaxation time was obtained by subtracting ejection time from the duration of tricuspid regurgitation. The Doppler RV index tended to be elevated (median 0.83) compared with normal ranges. Normal Doppler RV index was 0.28 +/- 0.04. After a mean follow-up duration of 2.9 years, 4 patients underwent lung transplantation and 30 patients died; the cause was cardiac in 28, noncardiac in 1, and uncertain in 1. Univariately, the Doppler RV index (chi-square 20.7, p <0.0001), severity of tricuspid regurgitation (chi-square 8.2, p = 0.004), treatment with calcium blockers (chi-square 6.6, p = 0.01), heart rate (chi-square 5.1, p = 0.02), and symptom status (chi-square 4.9, p = 0.03) were associated with adverse outcome (cardiac deaths and lung transplantation). However, only the Doppler RV index and treatment with calcium blockers were independent predictors within the multivariate model. Our results indicate that the Doppler RV index is a useful predictor of adverse outcome in patients with primary pulmonary hypertension.

Clinical profile and outcome in 52 patients with cardiac pseudoaneurysm

BACKGROUND

Cardiac pseudoaneurysm, a contained cardiac rupture, predisposes patients to further rupture. However, knowledge of the clinical profile and natural history of this cardiac complication is limited.

OBJECTIVE

To study the clinical features and outcomes of patients with cardiac pseudoaneurysm.

DESIGN

Retrospective analysis of patients with cardiac pseudoaneurysm seen between January 1980 and September 1996.

SETTING

Mayo Clinic in Rochester, Minnesota; Scottsdale, Arizona; and Jacksonville, Florida.

PATIENTS

52 patients with pseudoaneurysm.

RESULTS

Pseudoaneurysm was discovered incidentally in 25 asymptomatic patients (48%). Four patients (8%) presented acutely (3 with acute myocardial infarction and 1 with cardiac tamponade). Other clinical presentations were congestive heart failure in 8 patients (15%), chest pain in 7 (13%), syncope or arrhythmia in 5 (10%), and systemic embolism in 3 (6%). Initial diagnostic tests were echocardiography in 32 patients, cardiac catheterization in 12, magnetic resonance imaging in 4, and computed tomography in 2. Diagnosis was made intraoperatively in two patients. Pseudoaneurysm occurred after cardiac surgery in 30 patients (58%) and after myocardial infarction in 22 (42%). Location of the pseudoaneurysm was primarily related to its cause: Pseudoaneurysm was located in the inferior or posterolateral wall in 18 of 22 patients (82%) after myocardial infarction, in the right ventricular outflow tract in 13 of 15 patients (87%) after congenital heart surgery, in the posterior subannular region of the mitral valve in 4 of 4 patients (100%) after mitral valve replacement, and in the subaortic region in 3 of 3 (100%) after aortic valve replacement. Forty-two patients (81%) had surgical repair (surgical mortality rate, 7%). Ten patients (19%) did not have surgery. Nineteen patients died after a median survival of 2.3 years (range, 3 days to 8.2 years): Eight died of noncardiac cause, 5 of congestive heart failure, 4 of acute myocardial infarction, and 2 of cardiac arrhythmia (ventricular tachycardia). No further cardiac ruptures were documented.

CONCLUSIONS

A substantial number of patients with pseudoaneurysm are asymptomatic. Although surgical repair is the treatment of choice, conservative management in selected patients with increased surgical risk seems reasonable because no deaths were caused by further rupture.

Hypertrophic cardiomyopathy with obstruction: important diagnostic clue provided by the direction of the mitral regurgitation jet

We present an unusual case of hypertrophic cardiomyopathy complicated by mitral regurgitation resulting from chordal rupture with flail posterior mitral leaflet. The diagnosis was suggested by the presence of an anteriorly directed mitral regurgitation jet on transthoracic color flow imaging, in addition to the typical posterolateral-lateral jet caused by systolic anterior mitral motion. The flail posterior leaflet was confirmed by transesophageal echocardiography, and the patient underwent mitral valve repair in addition to myectomy. This combination of hypertrophic cardiomyopathy and flail mitral leaflet usually requires surgical intervention, and prompt diagnosis is important. The presence of an anteriorly directed mitral regurgitant jet should always raise suspicion of posterior mitral leaflet abnormality.

Retained left atrial catheter: an unusual cardiac source of embolism identified by transesophageal echocardiography

Embolic events have become a major indication for transesophageal echocardiography. We report three patients with cerebrovascular accident who were discovered to have retained left atrial catheter as a cardiac source of embolism. These radiolucent catheters, placed during previous cardiac surgery, were used for perioperative left atrial monitoring. Fracture of the catheter occurred during percutaneous removal after surgery. Subsequent identification was established by transesophageal echocardiography, which demonstrated a characteristic appearance of the catheter remnant within the left atrium. All patients underwent reoperation to remove the retained catheter and have had no recurrent embolic events. Although uncommon, retained catheter in the left atrium is an important potential source of systemic embolism. The diagnosis can be easily made with transesophageal echocardiography and should prompt surgical extraction of the catheter.

A case of unusual electrocardiographic presentation of right ventricular myocardial infarction

This is a case of an unusual electrocardiographic manifestation of a patient with right ventricular (RV) myocardial infarction occurring in association with left ventricular inferoposterior myocardial infarction. There was massive ST-segment elevation in the precordial leads resembling that of an anterior myocardial infarct in addition to the ST-segment elevation seen normally in right ventricular leads. Two-dimensional echocardiography confirmed right ventricular hypokinesia and coronary angiography revealed single-vessel coronary artery disease involving the right coronary artery. It served to remind us that the presence of diffuse and massive ST-segment elevation in the precordial leads in a patient with inferior myocardial infarction may indicate simultaneous RV infarction and warrants further confirmatory tests.

Electrocardiographic abnormalities in right ventricular infarction associated with right bundle branch block

An 80-year-old woman with pre-existing complete right bundle branch block presented with severe chest pain. The 12-lead electrocardiogram, together with right-sided chest leads, showed complete right bundle branch block and ST segment elevation in leads II, III, aVF, V5, V6 and V4R to V6R. These electrocardiographic abnormalities indicate acute 'Q wave' inferolateral and right ventricular infarction coexisting with right bundle branch block.

Dobutamine stress echocardiography in the elderly Asian patients

Dobutamine stress echocardiography (DSE) is an established non-invasive technique for the evaluation of coronary artery disease (CAD). It has been shown to be both safe and accurate. However, its utility and safety in the elderly, in particular, elderly Asian patients has not been studied. Between September 1992 and December 1994, we performed a total of 75 consecutive DSE studies in patients over the age of 65. Of these, 50 (67%) were females. Forty-nine patients had hypertension, 26 had diabetes mellitus, 10 were smokers, 5 had a recent or previous myocardial infarction and another 4 had a history of heart failure. Indications for DSE were, inability to perform the standard treadmill exercise test (40 patients), an abnormal resting electrocardiogram (ECG) (14 patients), a prior false positive or inconclusive treadmill test, risk stratification post myocardial infarction (4 patients) or preoperative cardiac evaluation (23 patients). The test was terminated in the majority of patients following attainment of the target heart rate. Atropine stimulation was required in 61 (81%) patients. Chest pain was provoked in 11 patients. No death or myocardial infarction occurred. Minor non-cardiac symptoms occurred in another 6 patients but this did not necessitate termination of the procedure. Three patients had transient hypotension, none of which was symptomatic. Arrhythmia occurred in 23 patients but the majority were isolated atrial or ventricular premature beats (20); 1 patient had atrial fibrillation and another developed transient junctional rhythm. Only one patient developed ventricular tachycardia but this was not haemodynamically significant and terminated easily with an intravenous dose of lignocaine. A conclusive result could be obtained in 72 (96%) patients. We concluded that DSE could be performed and interpreted in the majority of elderly Asian patients studied. Despite supplemental atropine, an aggressive dosing protocol and the inclusion of patients with a myocardial scar or history of heart failure, adverse effects were rare and often did not require any specific therapy.

Clinical and echocardiographic features of mitral valve prolapse patients in a local population

Mitral valve prolapse (MVP) is a commonly diagnosed condition with varied clinical presentations but local data is lacking. In our study, we reviewed 98 patients (54 males, 44 females) with echocardiographic mitral valve prolapse diagnosed between 1991 and 1993 to study the clinical profile and echocardiographic features of patients with this condition in our local population. The mean and median age at presentation/detection were 42 years and 38 years respectively. The majority of the patients were asymptomatic (59%); the rest presented with palpitations (21%), congestive heart failure (4%) and infective endocarditis (5%). On clinical examination, 64 patients had mitral regurgitation (13 patients had both mitral regurgitation murmur and a systolic click), while one or more systolic clicks were heard in another 32 patients. Six patients also had associated Marfan syndrome. 2D echo revealed isolated anterior and posterior leaflet involvement in 55 and 19 patients respectively. Another 24 patients had involvement of both leaflets. Mitral regurgitation was detected on colour Doppler study in 78 patients. Nine patients had associated tricuspid valve prolapse. Of the 98 patients, 8 patients developed flail mitral valve. Four were detected at presentation/diagnosis, while the other 4 were diagnosed incidentally on routine follow-up 2D echo. Of these 8 patients, one developed cardiac failure. The patients had been on follow-up for a mean period of 9 months. During this period, mitral regurgitation progressed in 3 patients resulting in valve surgery. Only 20 patients had arrhythmias detected on ambulatory ECG monitoring, most of them were frequent atrial and ventricular premature beats. No patient was found to have haemodynamically significant arrhythmia. In summary, most patients with MVP had anterior mitral valve leaflet prolapse and mitral regurgitation. Although most patients with MVP are asymptomatic or have minor symptoms, it is associated with significant morbidity.

Dobutamine stress echocardiography: angiographic correlates

We started a dobutamine stress echocardiography (DSE) programme in September 1992. Until January 1994, we had performed 300 such procedures. Of these patients, 81 underwent cardiac catheterisation within 6 months of DSE without a cardiac event in the interim. Eleven DSEs were performed to assess myocardial viability and another 6 were inconclusive for myocardial ischaemia. The remaining 64 were correlated with the angiographic data to determine the utility of this technique in our institution. The mean age of the cohort was 57 years. Thirty-six patients were referred for DSE in the workup for chest pain, either anginiform (22) or atypical (14). Fourteen patients had a recent (6) or remote (8) myocardial infarction. Thirteen patients were asymptomatic. Significant obstructive coronary artery disease (CAD) was identified in 36 patients of whom 17 and 19 had single and multivessel disease respectively. The sensitivity of DSE in the entire cohort was 89% and the specificity 82%. Positive and negative predictive values of DSE were 86% and 85% respectively. Although the numbers involved were small, sensitivity figures for single and multivessel disease were 94% and 84% respectively. Of the patients with single vessel CAD, prediction of the artery involved by presumed territorial supply was accurate in 81%. DSE is a highly accurate tool for evaluating CAD, identifying both the patient with CAD and the location of disease.

Cloning of a mineral phosphate-solubilizing gene from Pseudomonas cepacia

We have recently shown that the ability of some gram-negative bacteria to dissolve poorly soluble calcium phosphates (Mps+ phenotype) is the result of periplasmic oxidation of glucose to gluconic acid via the quinoprotein glucose dehydrogenase (GDH), a component of the direct oxidation pathway. Escherichia coli K-12 derivatives synthesize apo-GDH but not the cofactor pyrroloquinoline-quinone (PQQ) essential for formation of the holoenzyme. Therefore, in the absence of exogenous PQQ, these strains do not produce gluconic acid and are Mps-. Evidence is presented to show that expression of a single 396-base Pseudomonas cepacia open reading frame (designated gabY) in E. coli JM109 (a K-12 derivative) was sufficient to induce the Mps+ phenotype and production of gluconic acid. We present the nucleotide sequence of this open reading frame which coded for a protein (GabY) with a deduced M(r) of 14,235. Coupled transcription-translation of a plasmid (pSLY4 or pGAB1) carrying gabY resulted in production of a protein with an M(r) of 14,750. Disruption of the open reading frame of gabY via site-directed mutagenesis changed the phenotype to Mps- and eliminated gluconic acid production. The deduced amino acid sequence of gabY has no apparent homology with those of previously cloned direct oxidation pathway genes but does share regions highly homologous with the histidine permease system membrane-bound protein HisQ as well as other proteins in this family. In the presence of 1 microM exogenous PQQ, both JM109(pSLY4) and JM109(pGAB1) produced 10 times as much gluconic acid as was seen with either the plasmid or exogenous PQQ alone.(ABSTRACT TRUNCATED AT 250 WORDS)