Performance of QUiPP App v.2 tool for prediction of preterm birth in asymptomatic high-risk women attending preterm specialist clinic: external validation study.

OBJECTIVE: To validate externally the QUiPP App v.2 algorithms in an independent cohort of high-risk asymptomatic women attending a preterm birth (PTB) surveillance clinic in Ireland. METHODS: This was a retrospective, single-center, observational study assessing discrimination and calibration of the QUiPP App v.2 at six predetermined clinical timepoints (PTB at < 30, < 34 and < 37 weeks of pregnancy and PTB within 1, 2 and 4 weeks of testing). Discrimination was assessed by estimating the area under the receiver-operating-characteristics curve (AUC) and sensitivity at fixed false-positive rates of 5%, 10% and 20%. Model calibration was assessed to evaluate the concordance between expected and observed outcomes. P-values < 0.05 were considered statistically significant. No adjustments for treatment effects were made. RESULTS: Overall, 762 women with 1660 PTB surveillance clinic visits using the QUiPP App v.2 between 2019 and 2022 were analyzed. The study population included 142 (18.6%) patients who later experienced PTB. The QuiPP App's performance in the prediction of short-term outcomes, such as birth within 1 week (AUC, 0.866 (95% CI, 0.755-0.955)), 2 weeks (AUC, 0.721 (95% CI, 0.569-0.854)) and 4 weeks (AUC, 0.775 (95% CI, 0.699-0.842)), and delivery at < 30 weeks (AUC, 0.747 (95% CI, 0.613-0.865)), was superior to its ability to predict longer-term outcomes (PTB at < 37 weeks: AUC, 0.631 (95% CI, 0.596-0.668)). Calibration was generally good for low-risk results, as the predicted risk in these patients tended to match the observed incidence. However, in women deemed to be at greater risk of PTB, the predicted probability superseded the observed incidence of PTB. CONCLUSIONS: The QUiPP App v.2 accurately discriminates women who are at short-term risk of PTB. A 'treatment paradox' may influence calibration in high-risk women. Further research is needed to ascertain if QuiPP treatment thresholds can be safely adjusted in women receiving prophylactic treatment to prevent PTB, and whether this improves the outcome. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Perinatal and neonatal outcomes of high-risk asymptomatic women from a specialist preterm birth surveillance clinic.

OBJECTIVES: To report the perinatal outcomes of high-risk asymptomatic women who attended a specialist preterm surveillance clinic (PSC) to undergo screening for spontaneous preterm birth (PTB) in Ireland. METHODS: Single center, retrospective cohort study of asymptomatic high risk women who attended the PSC between January 2019 and December 2022. A comprehensive database of all patients who attended the clinic during the study period was constructed and analyzed. Overall outcomes were reported, and stratified per the occurrence of preterm or term birth. Iatrogenic PTBs were included in the outcome data. RESULTS: Following exclusions for loss-to-follow-up, 762 cases were analyzed, constituting 2262 PSC visits. Of those, 183 women were prescribed progesterone (24.0 %), and 100 women underwent cervical cerclage (13.1 %) to prevent spontaneous PTB. Overall, 2.4 %, 6.2 % and 18.6 % of participants gave birth prior to 30 weeks, 34 weeks, and 37 weeks, respectively. The median gestational age at birth for the entire cohort was 38.6 weeks (inter-quartile range (IQR) 37.2-39.6 weeks). Women who delivered < 37 weeks were significantly more likely to be smokers (p = 0.030), have a previous spontaneous PTB (p = 0.016), have multiple pregnancies (p < 0.001), type 1 or 2 diabetes (p = 0.044), or have a previous full dilatation caesarean section birth (p = 0.024). Infants born prior to 37 weeks were more likely to have a lower median birthweight (2270 vs 3300 g, p < 0.001), be admitted to a neonatal intensive care unit (53.8 % vs 2.3 %, p < 0.001) or experience short-term morbidity, including respiratory support (38.0 % vs 1.6 %, p < 0.001). CONCLUSIONS: Over 80% of women deemed to be at high risk of PTB gave birth at term gestations following attendance at a PSC during pregnancy. Most women can be successfully managed without interventions, instead employing a policy of serial cervical surveillance, to identify those at greatest risk of PTB.

Homelessness in pregnancy.

OBJECTIVES: To evaluate the association, if any, of homelessness or refuge accommodation on delivery and short term perinatal outcomes in an Irish tertiary maternity hospital. METHODS: A retrospective cohort study of 133 singleton pregnancies in women reporting to be homeless or living in refuge at their booking antenatal appointment between 2013 and 2022. Analysis compared sociodemographic characteristics and perinatal outcomes in this cohort to a reference population of 76,858 women with stable living arrangements. RESULTS: Women in the homeless/refuge population were statistically more likely to be single (75.2 % vs 39.5 %, p < 0.001), have an unplanned pregnancy (73.7 % vs 27.2 %, p < 0.001), report a history of psychiatric illness (42.9 % vs 22.4 %, p < 0.001), domestic violence (18.8 % vs 0.9 %, p < 0.001) alcohol consumption in pregnancy (3.0 % vs 0.8 %, p < 0.001) or smoking in pregnancy (41.3 % vs 9.7 %, p < 0.001). They were significantly more likely to have a preterm birth (adjusted OR 1.71 (1.01-2.87) p = 0.04). They also had a significantly lower median birth weight compared to the reference population (birthweight 3270 g vs 3420 g, p < 0.001). CONCLUSION: Women in the homeless and refuge population are more likely to experience poorer perinatal outcomes compared to women with stable living arrangements.

A cross-sectional survey of women's views and preferences for preterm birth screening and treatment.

OBJECTIVES: Primary outcomes were to determine; 1) the desire for more patient information from healthcare professionals on preterm birth (PTB) prevention 2) the desire for PTB screening surveillance or participation in research or 3) the acceptability of transvaginal ultrasound (TVUS) or vaginal examinations to predict spontaneous PTB. METHODS: A 19-question, piloted, self-administered survey was completed by unselected pregnant women in a tertiary maternity hospital in Dublin, Ireland. Data was collected to include maternal socio-demographics, past obstetric history, and current pregnancy details, in addition to views and preferences on PTB screening and preventative treatments. Statistical analysis to include binary and multinomial regression was performed by IBM SPSS Statistics for Windows (Version 29.0). RESULTS: 277 women completed the study survey. 9.4% of women had attended the preterm birth surveillance clinic (PSC). 75.1% of respondents indicated a preference for more information from healthcare professionals about PTB. 65% reported that TVUS and vaginal examinations were acceptable in pregnancy. The acceptability of antenatal examinations was significantly influenced by ethnicity; white European (OR 2.58, CI 1.12-5.95, p = 0.003) and Asian (OR 3.39, CI 1.18-9.67, p = 0.02). Discomfort (25.3%) and vaginal bleeding (11.9%) were the most frequently reported concerns about TVUS. 95.7% of unselected women indicated that they would accept treatment to prevent PTB. Vaginal progesterone (53.8%) was preferred treatment compared to cervical cerclage (15.9%) or cervical pessary (16.6%). 55.6% of respondents stated they attend or wish to attend for additional appointments or research opportunities for PTB screening. Women with a previous PTB or second trimester miscarriage were more likely to attend or wish to attend for PTB screening (OR 3.23, CI 1.34-7.79, p = 0.009). CONCLUSION: PTB is an important healthcare priority for pregnant women in Ireland. However, women require more information, counselling and reassurance about the utility and safety of TVUS in PSCs.

The duration of labor in spontaneous preterm deliveries: A retrospective observational study in a tertiary Irish maternity hospital.

BACKGROUND: Preterm deliveries account for 10% of all births, and are the most important cause of neonatal mortality globally. Despite their frequency, there is a paucity of information known about usual patterns of preterm labor, as previous studies which critically defined the normal progression of labor excluded preterm gestations. OBJECTIVE: To compare the durations of the first, second and third stages of spontaneous preterm labor in nulliparous and multiparous women at varying preterm gestations. METHODS: A retrospective observational study was undertaken of women admitted in spontaneous preterm labor from January 2017 to December 2020 with viable singleton gestations between 24 and 36 + 6 weeks' gestation who then proceeded to have a vaginal delivery. There were 512 cases following exclusion of preterm inductions of labor, instrumental vaginal deliveries, provider-initiated pre-labor Caesarean sections and emergency intrapartum Caesarean sections. The data was then examined to determine our outcomes of interest including the durations of the first, second and third stages of preterm labor, analyzing results by parity and gestation. For comparison, we reviewed data of term spontaneous labors and spontaneous vaginal deliveries during the same study period, identifying 8339 cases. FINDINGS: 97.6% of participants achieved a spontaneous cephalic vaginal delivery with the remainder undergoing an assisted breech birth. 5.7% of gestations delivered spontaneously between 24 + 0 and 27 + 6 weeks, with most births at gestations greater than 34 weeks (74%). The second stage duration (mean 15 vs 32 vs 32 mins respectively) was significantly different across the three gestation periods (p < 0.05), but was notably much quicker in extremely preterm labors. The first and third stage durations were similar between all gestational age groups with no statistically significant differences in results. There was a significant influence of parity on the first and second stages of labor, with multiparous women progressing more quickly than nulliparae (p < 0.001). CONCLUSION: The duration of spontaneous preterm labor is described. Multiparous women progress more quickly in the first and second stages of preterm labor than nulliparous women.

Cell free DNA screening for fetal aneuploidy in Ireland: An observational study of outcomes following insufficient fetal fraction.

OBJECTIVES: To determine maternal factors associated with low fetal fraction (FF). To determine the proportion of women who receive a result from repeat non-invasive prenatal testing (NIPT) testing. To identify any significant associations between pregnancy interventions or outcomes and low FF. STUDY DESIGN: Retrospective observational study of 4465 women undergoing antenatal screening by targeted cell free DNA (cfDNA) testing at an Irish tertiary maternity hospital between January 2017 and December 2022. Patients who failed to obtain a result after the first NIPT were analyzed in two cohorts; those who received a result on a repeat sample and those who failed to ever achieve a result despite a second, third or fourth cfDNA test. RESULTS: Risk of insufficient FF significantly increased with elevated maternal BMI (OR 1.07; 95% CI 1.01-1.13, p = 0.03) and in-vitro fertilization (IVF) (OR 3.4; 95% CI 1.19-9.4, p = 0.02). Women with no result were more likely to have diagnostic invasive testing (p < 0.01), but had no increased risk of aneuploidy. Repeated failed NIPT attempts due to low FF were significantly associated with the subsequent development of hypertensive diseases of pregnancy (p = 0.03). Greater than 70% of patients who were unsuccessful in a first or second attempt at NIPT due to low FF yielded a result following a second or third sample. CONCLUSIONS: High BMI and IVF conceptions are greater contributors to low FF than fetal aneuploidy. Repeating NIPT yields a result in greater than 70% of cases. WHAT'S ALREADY KNOWN ABOUT THIS TOPIC?: Fetal fraction (FF) in prenatal cfDNA testing is influenced by maternal and pregnancy factors including body mass index (BMI) and IVF. Low FF has been associated with adverse pregnancy outcomes including fetal aneuploidy and hypertensive diseases of pregnancy. WHAT DOES THIS STUDY ADD?: In a large Irish population, increasing maternal BMI and in-vitro fertilization are the most significant contributors to repeated test failures due to low FF. Greater than 70% of patients with test failure due to low FF will receive a result on 2nd and 3rd NIPT attempts. Patients with no result from NIPT were more likely to undergo diagnostic invasive testing but the risk of aneuploidy was not significantly increased.

A retrospective observational study of labour ward work Intensity: The challenge of maternity staffing.

BACKGROUND: The UK and Ireland are facing significant challenges in the recruitment and retention of midwifery staff. Deficiencies in staffing, training and leadership have been cited as contributory factors to substandard care in both regional and global independent maternity safety reports. Locally, workforce planning is critical to maintaining 'one to one' care for all women in labor and to meet the peaks of daily birthing suite activity. OBJECTIVES: Analyze the variation in work intensity, defined by the mean number and range of births per midwifery working hours. METHODS: Retrospective observational study of birthing suite activity between 2017 and 2020. 30,550 singleton births were reported during the study period; however, 6529 elective Cesarean sections were excluded as these were performed during normal working hours by a separate operating theatre team. The times of 24,021 singleton births were organized into five proposed midwifery working rosters lasting eight or 12 h; A (00.00-07.59), B (08.00-15.59), C (16.00-23.59), D (20.00-0.759) and E (0.800-19.59). RESULTS: The number of births was comparable between the eight-hour and 12-hour work periods with a mean of five to six babies born per roster (range zero to 15). Work periods D and E lasting 12-hours both recorded a mean of eight births (range zero to 18). Hourly births ranged from a minimum of zero to a maximum of five births per hour (greater than seven times the mean), a number that was achieved 14 times during the study period. CONCLUSIONS: The mean number of births is consistent between normal working hours and unsociable 'on-call' periods, however there is an extreme range of activity within each midwifery roster. Prompt escalation plans remain essential for maternity services to manage unexpected increases in demand and complexity. WHAT IS ALREADY KNOWN ON THIS TOPIC: Shortfalls in staffing and inadequate workforce planning have been frequently cited in recent maternity safety reports as barriers to sustainable and safe maternity care. WHAT THIS STUDY ADDS: Our study shows that the mean number of births in a large tertiary center are consistent across day and night rosters. However, there are large fluctuations in activity during which births can exceed the number of available midwives. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY: Our study reflects the sentiments of the Ockenden review and APPG report on safe maternity staffing. Investment in services and the workforce to aid recruitment and reduce attrition is essential to establish robust escalation plans, including the deployment of additional staff in the event of extreme service pressures.

Reexploration for bleeding is a risk factor for adverse outcomes after cardiac operations.

OBJECTIVE: Although previous studies have included early reexploration for bleeding as a risk factor in analyzing adverse outcomes after cardiac operations, reexploration for bleeding has not been systematically examined as a multivariate risk factor for increased morbidity and mortality after cardiac surgery. Furthermore, multivariate predictors of the need for reexploration have not been identified. Accordingly, we performed a retrospective analysis of 6100 patients requiring cardiopulmonary bypass from January 1, 1986, to December 31, 1993. METHODS: Eighty-five patients who had ventricular assist devices were excluded from further analysis because of the prevalence of bleeding and the significant morbidity and mortality associated with placement of a ventricular assist device, unrelated to reexploration. In the remaining 6015 patients, potential adverse outcomes analyzed included operative mortality, mediastinitis, stroke, renal failure, adult respiratory distress syndrome, prolonged mechanical ventilation, sepsis, atrial arrhythmias, and ventricular arrhythmias. To control for the confounding effects of other risk factors, we performed a multivariate logistic regression analysis. Potential covariates considered in the logistic model included age, sex, race, history of reoperation, urgency of the operation, congestive heart failure, prior myocardial infarction, renal failure, diabetes, hypertension, chronic obstructive pulmonary disease or stroke, and the bypass and crossclamp time. RESULTS: The overall incidence of reexploration was 4.2% (253/6015). Four independent risk factors--increased patient age (p < 0.001), preoperative renal insufficiency (p = 0.02), operation other than coronary bypass (p < 0.001), and prolonged bypass time (p = 0.0.3)--were identified as predictors of the need for reexploration. The preoperative use of aspirin, heparin, or thrombolytic agents and the bleeding time were not identified as predictors. Reexploration for bleeding was identified as a strong independent risk factor for operative mortality (p = 0.005), renal failure (p < 0.0001), prolonged mechanical ventilation (p < 0.0001), adult respiratory distress syndrome (p = 0.03), sepsis (p < 0.0001), and atrial arrhythmias (p = 0.006). CONCLUSION: These data indicate that meticulous attention to surgical hemostasis and possibly application of recently developed modalities designed to facilitate perioperative correction of coagulopathy could improve outcomes after cardiac operations.

Swallowing dysfunction after cardiac operations. Associated adverse outcomes and risk factors including intraoperative transesophageal echocardiography.

The frequency, importance to patient outcomes, and independent predictors of postoperative swallowing dysfunction documented by barium cineradiography were examined in 869 patients undergoing cardiac operations over a 12-month period. Swallowing dysfunction was diagnosed in 34 patients (4% incidence) and was associated with documented pulmonary aspiration in 90% of these patients, increased frequency of pneumonia (p < 0.0001), need for tracheostomy (p = 0.0002), length of stay in the intensive care unit (p = 0.0001), and duration of hospitalization after the operation (p = 0.0001). Independent predictors of postoperative swallowing dysfunction determined by multivariate logistic regression included age (p < 0.001), length of tracheal intubation after the operation (p = 0.001), and intraoperative use of transesophageal echocardiography (p = 0.003). Dysfunctional swallowing after cardiac operations, a serious complication significantly related to postoperative respiratory morbidity and extended length of hospitalization, is more common in older patients. An association between intraoperative use of transesophageal echocardiography and swallowing dysfunction was also observed in our patients.

Hazards of postoperative atrial arrhythmias.

Between January 1, 1986, and December 31, 1991, 4,507 adult patients underwent cardiac surgical procedures requiring cardiopulmonary bypass. Of these patients, 3,983 patients who did not undergo operation for supraventricular tachycardia and who were in normal sinus rhythm preoperatively form the study group for the present study. Postoperatively, all patients were monitored continuously for the development of arrhythmias until the time of hospital discharge. The incidence of atrial arrhythmias requiring treatment for the most commonly performed operative procedures were as follows: coronary artery bypass grafting, 31.9%; coronary artery bypass grafting and mitral valve replacement, 63.6%; coronary artery bypass grafting and aortic valve replacement, 48.8%; and heart transplantation, 11.1%. For all patients considered collectively, the risk factors associated with an increased incidence of postoperative atrial arrhythmias (p < 0.05 by multivariate logistic regression) included increasing patient age, preoperative use of digoxin, history of rheumatic heart disease, chronic obstructive pulmonary disease, and increasing aortic cross-clamp time. Postoperative atrial fibrillation was associated with an increased incidence of postoperative stroke (3.3% versus 1.4%; p < 0.0005), increased length of hospitalization in the intensive care unit (5.7 versus 3.4 days; p = 0.001) and postoperative nursing ward (10.9 versus 7.5 days; p = 0.0001), increased incidence of postoperative ventricular tachycardia or fibrillation (9.2% versus 4.0%; p < 0.0005), and an increased need for placement of a permanent pacemaker (3.7% versus 1.6%; p < 0.0005). These data provide a basis for targeting specific patient subgroups for prospective, randomized trials of therapeutic modalities designed to decrease the incidence of postoperative atrial arrhythmias.

Revascularization after acute myocardial infarction.

BACKGROUND: The optimal timing for coronary artery bypass grafting (CABG) after acute myocardial infarction (MI) remains controversial. METHODS: We examined our experience retrospectively in 3,942 patients who underwent CABG between 1986 and 1993, including 2,296 patients after acute MI. RESULTS: The operative mortality associated with increasing time intervals between MI and CABG were 9.1%, 8.3%, 5.2%, 6.5%, and 2.9%, for less than 6 hours, 6 hours to 2 days, 2 to 14 days, 2 to 6 weeks, and more than 6 weeks, respectively. In comparison, the operative mortality was 2.5% for patients with no history of acute MI. The incidence of permanent stroke and perioperative MI were greater and the length of postoperative hospitalization was longer for patients undergoing CABG early after MI. For patients undergoing operation electively, however, the operative mortality associated with increasing time intervals between MI and CABG were less, at 0.0%, 3.6%, 2.1%, 6.4%, and 2.1% for less than 6 hours, 6 hours to 2 days, 2 to 14 days, 2 to 6 weeks, and more than 6 weeks, respectively. For patients undergoing CABG within 14 days of MI, the operative mortality was 5.3% for those receiving an intraaortic balloon pump preoperatively for postinfarction angina, but 11.8% for those who underwent urgent/emergent operation without intraaortic balloon pump support. CONCLUSIONS: Elective CABG can be accomplished with acceptable morbidity and mortality early after acute MI if an elective operation is possible. In addition, the intraaortic balloon pump should be used aggressively in patients with postinfarction angina to allow for elective rather than urgent/emergent operation.

Coronary artery disease in patients with type A aortic dissection.

The usefulness of preoperative coronary arteriography in patients with type A dissection of the aorta is controversial. To determine the prevalence of arteriosclerotic coronary artery disease in patients with type A dissection of the aorta, we reviewed our experience in 62 patients (42 with acute dissection and 20 with chronic dissection) who underwent operation between January 1, 1986, and December 31, 1993. Among 23 patients with acute dissection who underwent coronary arteriography, 8 (34.8%) had one or more coronary artery lesions causing a greater than 50% narrowing. Among 14 patients with chronic dissection who underwent coronary arteriography, 6 (42.9%) had one or more coronary artery lesions causing a greater than 50% narrowing. There were no fatal complications associated with coronary arteriography. Four patients with acute dissection and 6 patients with chronic dissection underwent coronary artery bypass grafting at the time of operative repair of the aortic dissection, with no operative deaths. On the basis of these findings and the success of combined coronary artery bypass grafting and aortic repair, we recommend that patients with an acute type A dissection who are in stable condition and all patients with a chronic type A dissection of the aorta should undergo preoperative coronary arteriography.

Potential ablation of accessory atrioventricular pathways: injection of alcohol into the atrioventricular groove.

Accessory atrioventricular (AV) pathways responsible for the Wolff-Parkinson-White syndrome have been treated successfully by surgical and radiofrequency catheter ablation techniques. In this study, we explored the feasibility of permanent chemical ablation of accessory pathways by direct injection of 100% ethanol into the canine AV groove. Right coronary artery blood flow and AV compartment pressure were measured in 5 adult mongrel dogs (part I) during injection of saline solution (10 to 15 mL) into the right AV groove. Atrioventricular groove compartment pressure increased from 1 +/- 1 to 31 +/- 12 mm Hg (p < 0.0001) and right coronary artery blood flow increased slightly from 117 +/- 17 to 138 +/- 44 mL/min (p = not significant). In 8 additional dogs (part II), 100% ethanol (10 mL) was injected into the left AV groove. After 6 weeks (n = 6) or 12 weeks (n = 2), histologic examination of the left AV groove demonstrated localized fibrous replacement of injured epicardial muscle, with only scant inflammatory infiltrate. Mild intimal fibrosis and intimal proliferation were present in the circumflex artery and its larger branches, but no significant luminal narrowing was evident. Angiograms at 12 weeks (n = 2) demonstrated no significant narrowing of the circumflex artery. In summary, injection of 100% ethanol into the AV groove is capable of locally ablating myocardial tissue, presumably including conductive tissues, while sparing the coronary arteries.

Regional myocardial stress distribution from magnetic resonance image-based mathematical models.

The instantaneous regional stress distribution within the myocardium, which cannot be directly measured, has been estimated using improved numerical methods and nonaxisymmetric biventricular geometry. To do this, we have employed computer-aided solid mathematical modeling to generate a three-dimensional representation for an ex vivo canine biventricular unit using magnetic resonance imaging. A two-dimensional transverse section was isolated from the solid mathematical model for regional stress analysis using p-version finite element analysis. Loading conditions and material property descriptions were taken from published reports. Analyses showed the maximum principal stresses to range from -1.76 X 10(5) to 8.52 X 10(5) dynes/cm2 during systolic loading, and from -3.85 X 10(4) to 1.13 X 10(5) dynes/cm2 during diastolic loading. This study demonstrates that magnetic resonance image-based solid mathematical biventricular models are suitable for regional stress analysis using p-version finite element analysis. p-Version finite element analysis using magnetic resonance image-based cardiac representations facilitates in vivo stress-strain analyses and may allow the clinical estimation of regional myocardial stress.

Mechanical dysfunction in the border zone of an ovine model of left ventricular aneurysm.

BACKGROUND: The pathophysiology of regional mechanical dysfunction in the border zone (BZ) region of left ventricular aneurysm was studied in an ovine model using magnetic resonance imaging tissue-tagging and regional deformation analysis. METHODS: Transmural infarcts were created in adult Dorsett sheep (n = 8) by ligation of the distal homonymous coronary artery and were allowed to mature into left ventricular aneurysms for 8 to 12 weeks. Animals were imaged subsequently using double oblique magnetic resonance imaging with radiofrequency tissue tagging. Short axis slices were selected for analysis that included predominantly the septal component of the aneurysm as well as adjacent BZ regions in the anterior and posterior ventricular walls. Dark grid patterns of magnetic presaturations were placed on the myocardium and tracked as they deformed during the diastolic, isovolumic systolic, and systolic ejection phases of the cardiac cycle. Regional ventricular wall strains were calculated in BZ regions and regions remote from the aneurysm and compared with strains measured in corresponding regions from normal control sheep (n = 6). RESULTS: Diastolic midwall circumferential strains (fiber extensions) were relatively preserved, but abnormal circumferential lengthening strains were observed in the BZ regions during isovolumic systole. Peak circumferential strains ranged from 0.04 to 0.07 in the BZ regions but averaged -0.05 in the normal hearts (p = 0.002 for the anterior BZ and p = 0.001 for the posterior BZ). Midwall end-systolic fiber strains were depressed in the anterior BZ (-0.03 to -0.09 for the BZ versus -0.11 for the normal heart, p < 0.0001) but not in the posterior BZ (p = 0.19). CONCLUSIONS: Our data support the theory that the stretching of BZ fibers during isovolumic systole contributed to a reduction in fiber shortening during systolic ejection and thus reduced the overall contribution of these fibers to forward ventricular output.

Intraaortic balloon counterpulsation: patterns of usage and outcome in cardiac surgery patients.

Between January 1, 1986, and May 6, 1991, 7,884 cardiac surgical procedures requiring cardiopulmonary bypass were performed at our institution, including 672 (9.8% of adult procedures) performed in 669 patients that were associated with preoperative (n = 240), intraoperative (n = 353), or postoperative (n = 79) use of an intraaortic balloon pump. The mean age of recipients was 65.3 years (range, 16 to 89 years). Intraaortic balloon pump usage increased during the study period from 6.4% of patients (83/1,298) in 1986 to 12.7% of patients (169/1,333) in 1990. The relative distribution between preoperative (mean, 35.7%), intraoperative (52.5%), and postoperative (11.8%) insertion remained nearly constant during the study period. The overall operative (30-day) mortality for patients with preoperative, intraoperative, or postoperative insertion of the intraaortic balloon pump was 19.6%, 32.3%, and 40.5%, respectively (X2 = 16.4; p less than 0.001). Although use of the intraaortic balloon pump in the intraoperative and postoperative settings is accompanied by a favorable outcome in most patients, the high associated mortality suggests the need for earlier use of the intraaortic balloon pump or other supportive measures such as the ventricular assist device.

Mathematical modeling of the heart using magnetic resonance imaging.

A hybrid three-dimensional solid mathematical model of cardiac ventricular geometry developed using magnetic resonance (MR) images of an in vivo canine heart is discussed. The modeling techniques were validated using MR images of an ex vivo heart and direct measurements of cardiac geometry and mass properties. A spin-echo MR sequence with in-plane resolution of 1.0 mm was used to image the canine heart in eleven short-axis planes at contiguous 5-mm intervals. Contour points on the epicardial, left ventricle (LV), and right ventricle (RV) boundaries were selected manually at each slice level. A boundary representation geometric model was constructed by fitting third-order nonuniform rational B-spline surfaces through each set of surface points. Compared to the anatomic specimen (AS), volume errors of the ex vivo model were 0.3, 1.5, and 5.8% for the LV cavity, RV cavity, and total enclosed volumes, respectively. Comparison of cross-sectional areas of the AS and the model at ten levels demonstrated mean model errors of 4.1, 2.5, and 2.9% for the LV, RV, and epicardial boundaries, respectively.

Postoperative atrial arrhythmias: risk factors and associated adverse outcomes.

Atrial arrhythmias are the most common complication of cardiac surgical procedures today. Because of the additional hospital costs associated with these arrhythmias, owing to increased use of antiarrhythmic medications, diagnostic studies, and prolonged hospitalization, this subject continues to draw the interest of cardiac surgeons, cardiologists, insurance companies, and hospital administrators, among others. Despite many clinical studies, there is still no consensus regarding the best prevention strategy for these arrhythmias. We recently reviewed our experience with these arrhythmias, with the intent of identifying risk factors for the development of these arrhythmias and identifying any associated, potentially adverse, outcomes. We found that the incidence of postoperative atrial arrhythmias has increased to more than 35% in recent years. Risk factors for the development of postoperative atrial arrhythmias include increasing patient age, preoperative use of digoxin, history of rheumatic heart disease, chronic obstructive pulmonary disease, and increasing aortic cross-clamp (ischemic) time. Among patients with postoperative atrial arrhythmias, there was an increased rate of perioperative stroke, increased frequency of ventricular arrhythmias, increased need for the placement of a permanent pacemaker, and prolongation of the intensive care unit and total hospital length of stay.

An inverse approach to determining myocardial material properties.

Passive myocardial material properties have been measured previously by subjecting test samples of myocardium to in vitro load-deformation analysis or, in the intact heart, by pressure-volume relationships. A new method for determining passive material properties, described in this paper, couples a p-version finite element model of the heart, a nonlinear optimization algorithm and a dense set of transmural measured strains that could be obtained in the intact heart by magnetic resonance imaging (MRI) radiofrequency tissue tagging. Unknown material parameters for a nonlinear, nonhomogeneous material law are determined by solving an inverse boundary value problem. An objective function relating the least-squares difference of model-predicted and measured strains is minimized with respect to the unknown material parameters using a novel optimization algorithm that utilizes forward finite element solutions to calculate derivatives of model-predicted strains with respect to the material parameters. Test cases incorporating several salient features of the inverse material identification problem for the heart are formulated to test the performance of the inverse algorithm in typical experimental conditions. Known true material parameters can be determined to within a small tolerance and random noise is shown not to affect the stability of the inverse solution appreciably. On the basis of these validation experiments, we conclude that the inverse material identification problem for the heart can be extended to solve for unknown material parameters that describe in vivo myocardial material behavior.

Ventricular interaction in the pathologic heart. A model based study.

The effects of direct ventricular interaction and interaction mediated by the pericardium on the diastolic left ventricle (LV) were quantified using idealized models of five pathologic conditions. Two-dimensional (2D) mathematical models were constructed in long and short axis views of four pathologic LV conditions and the normal heart (NL): dilated cardiomyopathy (DCM), concentric LV hypertrophy (HYP), chronic anterior-apical infarction in a normal shaped LV (CAINL), and CAI in a dilated LV (CAID). To assess the effects of RV pressure increase on the LV mechanical state, RV pressure was systematically increased for several LV pressures and changes in the LV diastolic pressure-area relationships, and LV free wall and septal principal stresses and strains were quantified. At higher RV pressures, with pericardial effects included in the models, the pressure-area relationship was similar for all models, indicating that, at these higher pressures, the effects of RV and pericardial pressures are more important than global LV shape, wall thickness, or material properties in determining the pressure-area relationship. There were significant differences among models in the changes in LV free wall and septal stress and strain after an increase in RV pressure. These models may be of use in predicting interaction in the corresponding clinical state.