Central hemodynamic assessment of normal term pregnancy

Cardiovascular responses to aerobic exercise during pregnancy and postpartum

The many physiological and hormonal changes occurring during pregnancy have the potential to affect a woman's cardiovascular responses to aerobic exercise. For example, it seems that increased mass and dilation of the left ventricle allow maintenance of wall stress, ensuring adequate pumping function throughout gestation. Also, a woman's cardiac output response to exercise is typically increased during pregnancy, owing to alterations in both heart rate and stroke volume. However, mean arterial pressure response is not usually affected by pregnancy because the increased blood flow to the uteroplacental unit, skin, and kidneys results in a concomitant decrease in systemic vascular resistance. It should be noted that there is no clear agreement on the mechanisms behind hemodynamic responses to exercise throughout gestation. Indeed, a pregnant woman's cardiac output during physical activity may be affected by (1) gestational age, (2) body position, (3) exercise intensity and modality, and (4) fitness level.

Coronary artery disease in insulin-dependent diabetes mellitus of pregnancy (class H): a review of the literature

Coronary heart disease and myocardial infarction are uncommon complications during pregnancy. Women with insulin-dependent diabetes mellitus (IDDM) have a much greater risk of serious coronary heart disease, but few cases of myocardial infarctions occurring during pregnancy have been reported. Significant maternal morbidity has been reported in half of these cases. This is a case of a myocardial infarction occurring at 21 weeks of gestation in a patient with class R/F IDDM and the subsequent pregnancy management as well as a review of the literature concerning Class H IDDM in pregnancy.

Pregnancy after cardiac transplantation: principles of nursing care

The number of cardiac transplants for chronic end-stage disease, congenital heart disease, and primary pulmonary hypertension has increased during the past 20 years. Decreased symptoms, decreased incidence of rejection, and greater tolerance of medical regimens have improved the quality of life for heart transplant recipients. Women of childbearing age who have undergone cardiac transplantation may now consider pregnancy. The principles of nursing care for pregnant women who have undergone heart transplantation are presented in this article. A case report of pregnancy after cardiac transplantation is included.

Anesthetic considerations for parturients with primary pulmonary hypertension: review of the literature and clinical presentation

Primary pulmonary hypertension, though uncommon, is found relatively frequently in women of childbearing age and carries a high peripartum mortality. We present a patient with severe primary pulmonary hypertension who underwent two cesarean sections 3 and 6 years after the diagnosis of primary pulmonary hypertension was made. Epidural anesthesia was provided on both occasions and resulted in a good maternal and fetal outcome. We have reviewed the literature as it relates to the choice of anesthetic technique and maternal outcome in patients with primary pulmonary hypertension.

Peripartum cardiomyopathy

Congestive heart failure is an uncommon complication of pregnancy with potentially life-threatening consequences. Peripartum cardiomyopathy is a disease of unknown cause in which severe left ventricular dysfunction occurs during late pregnancy or the early puerperium. In the past, the diagnosis of this entity was made on clinical grounds; however, modern echocardiographic techniques have allowed more accurate diagnoses by excluding cases of diseases that mimic the clinical symptoms and signs of heart failure. Risk factors for peripartum cardiomyopathy include advanced maternal age, multiparity, African descent, twinning, and long-term tocolysis. An extensive search for the causes of peripartum cardiomyopathy has been unrevealing. Treatment includes digitalis, diuretic agents, and vasodilators. Anticoagulation is strongly recommended, especially if ventricular function is persistent. The prognosis of peripartum cardiomyopathy is related to the recovery of ventricular function. Caution is advised in recommending subsequent pregnancy, especially if left ventricular dysfunction is persistent.

Hepatic venous Doppler waveforms: changes in pregnancy

A total of 75 fasted healthy normal volunteers were examined during various stages of pregnancy. Examinations were performed in a supine position using an Acuson 128 ultrasound scanner with a 3.5 MHz transducer. Doppler interrogation of the middle hepatic vein was made during quiet respiration by one of three examiners. The Doppler waveforms were subsequently assessed blindly by one of the authors and categorized as normal, damped, or flat. Between 12 and 20 weeks, the majority of patients had normal hepatic pulsatility (64%) with 20% damped and 16% flat. Between 20 and 30 weeks there was a significant change (p > 0.001) with 68% being flat, 20% damped, and only 12% normal. In the last 10 weeks of pregnancy the changes were more marked: 80% were flat, 12% dampened, and 8% normal. There was a profound change in hepatic venous pulsatility during pregnancy. Hepatic waveforms changed from their normal pulsatile nature to become completely flat with increasing gestation. These changes were more frequent and more marked the further gestation progressed.

Mitral stenosis: implications for critical care obstetric nursing

Pregnancy complicated by mitral stenosis poses a significant risk for maternal morbidity and mortality. The perinatal nurse is challenged to use obstetric and cardiac physiologic principles in planning and guiding care during the intrapartum period. Nursing assessments and interventions based on these principles promote positive outcomes.

Amniotic fluid embolism: analysis of the national registry

OBJECTIVE

We analyzed the clinical course and investigated possible pathophysiologic mechanisms of amniotic fluid embolism.

STUDY DESIGN

We carried out a retrospective review of medical records. Forty-six charts were analyzed for 121 separate clinical variables.

RESULTS

Amniotic fluid embolism occurred during labor in 70% of the women, after vaginal delivery in 11%, and during cesarean section after delivery of the infant in 19%. No correlation was seen with prolonged labor or oxytocin use. A significant relation was seen between amniotic fluid embolism and male fetal sex. Forty-one percent of patients gave a history of allergy or atopy. Maternal mortality was 61%, with neurologically intact survival seen in 15% of women. Of fetuses in utero at the time of the event, only 39% survived. Clinical and hemodynamic manifestations were similar to those manifest in anaphylaxis and septic shock.

CONCLUSIONS

Intact maternal or fetal survival with amniotic fluid embolism is rare. The striking similarities between clinical and hemodynamic findings in amniotic fluid embolism and both anaphylaxis and septic shock suggest a common pathophysiologic mechanism for all these conditions. Thus the term amniotic fluid embolism appears to be a misnomer.

Plasma levels of atrial natriuretic peptide in normal and hypertensive pregnancies: a meta-analysis

OBJECTIVE

Our goals were (1) to use meta-analysis to determine whether pregnancy and the puerperium are accompanied by alterations in plasma atrial natriuretic peptide levels when compared with the nonpregnant state and (2) to evaluate the additional effects of hypertensive disease during pregnancy on plasma atrial natriuretic peptide levels.

STUDY DESIGN

Articles measuring atrial natriuretic peptide levels during pregnancy were reviewed. Data from articles meeting inclusion criteria were abstracted, and a meta-analysis was performed with the use of the maximum likelihood methods of Jennrich and Schluchter (Biometrics 1986;42:805-20).

RESULTS

The mean atrial natriuretic peptide level in nonpregnant control subjects was 28.7 pg/ml (95% confidence interval 22.5 to 36.7). The mean plasma atrial natriuretic peptide level rose 41% to 40.5 pg/ml (95% confidence interval 31.7 to 51.8) in the third trimester (p < 0.0001). It was 71.1 pg/ml (95% confidence interval 51.2 to 98.7) or 148% greater than the mean nonpregnant level during the first week post partum (p < 0.0001). Compared with levels in pregnant control subjects, plasma atrial natriuretic peptide levels increased 52% to 52.1 pg/ml (95% confidence interval 32.9 to 82.5) in women with gestational hypertension (p < 0.005) and 130% to 78.8 pg/ml (95% confidence interval 52.3 to 118.8) in women with preeclampsia (p < 0.0001). Chronic hypertension did not significantly alter atrial natriuretic peptide levels.

CONCLUSIONS

The 41% increase in atrial natriuretic peptide levels in the third trimester suggests that atrial stretch receptors sense the expanded blood volume as normal to moderately increased. The rise in atrial natriuretic peptide during the first week post partum is consistent with known hemodynamic changes and suggests that atrial natriuretic peptide may be involved in the postpartum diuresis. The marked increase in plasma atrial natriuretic peptide levels observed in preeclampsia is not likely to result from elevated arterial pressures alone but may reflect underlying factors unique to this disease process.

A longitudinal study of cardiac output in normal human pregnancy

OBJECTIVE

Our purpose was to investigate the maternal hemodynamic and cardiac structural changes that occur during pregnancy.

STUDY DESIGN

Eighteen women underwent serial echocardiography beginning at 8 to 11 weeks' gestation, then at monthly intervals throughout pregnancy and at 6 and 12 weeks post partum. Cardiac output was measured by pulsed- and continuous-wave Doppler at the aortic valve. Left ventricular chamber size, wall thickness, and mass were determined by M-mode echocardiography. Ventricular diastolic function was assessed by Doppler recording of mitral inflow.

RESULTS

Cardiac output by pulsed Doppler increased from 6.7 +/- 0.6 L/min at 8 to 11 weeks' gestation to 8.7 +/- 1.4 L/min at 36 to 39 weeks' gestation before falling to 5.7 +/- 0.7 L/min 12 weeks post partum. Heart rate increased 29%, and stroke volume increased 18%. Left ventricular mass increased because of an increase in wall thickness. Peak mitral A wave velocity increased in late pregnancy. Cardiac output by pulsed and continuous-wave Doppler was similar.

CONCLUSION

Cardiac output continues to increase even in late pregnancy. Left ventricular mass increases because of increased wall thickness. The mitral flow velocity findings suggested decreased ventricular compliance or increased preload.

Acute hemodynamic and respiratory effects of amniotic fluid embolism in the pregnant goat model

OBJECTIVE

Our purpose was to determine the acute-phase central hemodynamic and respiratory effects of raw, filtered, filtered and boiled, and meconium-containing amniotic fluid.

STUDY DESIGN

Pregnant goats (Capra hircus) in the last one third of pregnancy were given freshly collected autologous amniotic fluid in a volume of 2.5 ml/kg of body weight. Observations were then made at 10, 30, 60, 120, and 180 minutes after amniotic fluid embolism. Pulmonary artery catheters and femoral artery lung water catheters were placed for specimen and data collection.

RESULTS

Marked pressor responses were observed in both the pulmonary and systemic circulations with all amniotic fluid infusions. The pressor response was similar with raw, filtered, and filtered and boiled amniotic fluid. The pressor response seen with amniotic fluid containing meconium was significantly greater than that seen with the other forms. No significant effects were observed on cardiac or respiratory function except in the meconium group, where transient left ventricular dysfunction was accompanied by an acute increase in extravascular lung water and dysoxia.

CONCLUSIONS

The Capra hircus model is appropriate for the further study of amniotic fluid embolism. The acute pressor effects are transient and involve both the systemic and pulmonary circulations. Left ventricular dysfunction and dysoxia were observed only with embolism of amniotic fluid containing meconium.

Aortic stenosis, cesarean delivery, and epidural anesthesia

A 23-year-old female was referred to the University of Arkansas for Medical Sciences at 32 weeks' gestation with a history of aortic stenosis following aortic valve replacement. Evaluation by echocardiography showed an approximately 90 mmHg transvalvular pressure gradient. Pregnancy progressed to 36 weeks' gestation without problem, at which time the patient underwent cesarean section with lumbar epidural anesthesia. Invasive hemodynamic monitors were used to assess cardiac performance and as a guide for anesthetic management. The impact of aortic stenosis on pregnancy is discussed, as are management aspects of lumbar epidural anesthesia in such patients.

Adaptation of the maternal heart in pregnancy

The first haemodynamic change during pregnancy seems to be a rise in heart rate. Starting between two and five weeks this continues well into the third trimester. Stroke volume increases slightly later than the heart rate and continues throughout the second trimester after an augmentation of venous return and a fall of systemic vascular resistance and afterload. Myocardial contractility is probably slightly increased. During the third trimester there is relatively little change in these cardiac indices. After delivery there is a very early and dramatic reduction in volume loading followed by a return towards normal cardiac output. Structural changes within the heart reflect the volume loading of pregnancy and include dilatation of the valve ring and increase in myocardial thickness. Post partum resolution of the ventricular hypertrophy seems to take longer than the rest of the post partum changes. The resemblance to the cardiovascular changes associated with training and exercise are fascinating and worthy of further study.

Arterial pressure response to maximal isometric exercise in pregnant women

We studied the arterial pressure response to maximal leg exercise in 15 healthy volunteers at 29 and 35 weeks' pregnancy and at 8 weeks post partum. Resting mean arterial pressure at 35 weeks' gestation was similar to the postpartum control value of 88 mm Hg (range 73 to 111), but it was reduced by 10% at 29 weeks' gestation. Voluntary maximal effort averaged 2470 N (range 1450 to 3030) in the postpartum period, was similar at 29 weeks, and was reduced by 13% at 35 weeks' gestation. Mean arterial pressure showed a linear increase with force to a median maximum value of 131 (104 to 159) mm Hg, or 49% above the resting value in the postpartum period. The pressure response was unaffected by pregnancy, but was inversely related to maximal force, i.e., the individual's capacity to perform isometric exercise.

Position change and central hemodynamic profile during normal third-trimester pregnancy and post partum

Central hemodynamic response to position change was assessed in 10 normotensive primiparous patients between 36 and 38 weeks' gestation. Studies were repeated between 11 and 13 weeks post partum. Compared with the left lateral position, we observed a mean 9% fall in cardiac output in the supine position and an 18% fall when patients were standing. When standing, these patients had a 30% increase in pulse and a 21% fall in left ventricular stroke work index. The orthostatic response after pregnancy was much more labile than that during the third trimester. These findings have important descriptive implications for the understanding of the human response to orthostasis during pregnancy, as well as clinical implications for patients at risk of uteroplacental insufficiency and for working women during pregnancy.