Special situations and conditions

CHAPTER 7 Special situations and conditions

7.1 PREGNANCY

Echo in pregnancy is safe. Many pregnant women develop systolic murmurs due to increased cardiac output (which rises by 30–50% in pregnancy). Many murmurs are benign (e.g. mammary souffle) but some may not be. Cardiac disease can present and be diagnosed for the first time during pregnancy, or those with pre-existing heart disease may become pregnant and may suffer deterioration in their cardiac state. Echo is essential in both situations. Some may suffer troublesome palpitations and whilst this is a less clear-cut indication for echo, the finding of normal LV function, chamber size and valve function can be very reassuring.

Anatomical and echo changes in pregnancy can include:

• Mild increases in cardiac chamber size including RA and RV. LA increases by 10–15% and LV by 5–10%.

• Increased stroke volume (increased flow velocity integral of AV and PV).

• Small pericardial effusions (20%) causing no haemodynamic compromise. If there is compromise, another cause must be sought.

• Peripartum cardiomyopathy.

• Vascular ‘laxity’ in peripartum period. Both aortic and coronary artery spontaneous dissections are more common, but still rare.

• In late pregnancy, the enlarged uterus may increase intra-abdominal pressure causing compression of the thoracic structures and a pseudo-posterior wall motion abnormality as occurs in liver disease with ascites.

Of course, there are a number of congenital cardiac abnormalities that have important implications for pregnancy.

The body of knowledge relating to high cardiac-risk pregnancies is increasing. Many women with such pregnancies are managed in specialized centres where a multidisciplinary team including obstetricians, midwives, cardiologists, anaesthetists, nurses and cardiac technicians work together to minimize the risks. Echo often plays an important part in the decision-making process.

1. Cardiac lesions associated with high risk (to mother)

• PHT (primary or secondary to Eisenmenger)

• Marfan’s syndrome

• HCM (especially if high degree of outflow tract obstruction)

• Any lesion causing New York Heart Association grade 4 breathlessness (i.e. at rest or on minimal exertion).

Eisenmenger’s reaction (PHT with a shunt) carries a high maternal (30–70%) and fetal mortality. Maternal mortality is due to arrhythmia, increased cyanosis, low cardiac output, catastrophic rise in PA pressure and right heart failure. The early postpartum period is particularly dangerous, possibly related to sudden alterations in venous return.

In AS or MS, pregnancy increases the valve gradient as cardiac output rises and systemic vascular resistance falls. MS can be very difficult in pregnancy. Echo allows noninvasive assessment of valve orifice and PA pressures and may help to determine timing of delivery or valvotomy.

In Marfan’s syndrome, the dominant hazard is aortic root dilatation and aortic dissection made more likely by haemodynamic changes and weakening of the aortic wall by hormonal changes.

Echo allows serial noninvasive assessment of PASP during pregnancy when this is elevated (e.g. primary or secondary to MV disease or Eisenmenger’s).

3. Lower-risk lesions are fortunately the most common

• Uncomplicated ASD or VSD, although there is a risk of paradoxical embolization. One particular problem of unoperated ASD or VSD occurs at delivery. Blood loss may lower RA pressure and increase left to right shunting, stealing from the systemic circulation, sometimes progressively and catastrophically. Intravenous fluid replacement must be rigorous in these patients.

• MR, AR and PS are usually well tolerated in pregnancy.

Benign maternal murmurs in pregnancy (see section 1.6)

• Pulmonary flow murmur – at left sternal edge at 2nd intercostal space. Due to increased cardiac output and flow into the pulmonary circulation

• Mammary souffle – associated with lactation and ceasing when that ends.

Peripartum cardiomyopathy

Echo shows a dilated LV with impaired systolic function. It presents in the later part of pregnancy and in the postpartum months. The echo features are identical to those of dilated cardiomyopathy. It may represent pre-existing dilated cardiomyopathy undiagnosed before pregnancy. The prognosis relates to the severity of heart failure and how rapidly cardiac size returns to normal. If present for more than 6 months, the prognosis is poor. Treatment is conventional (diuretics and ACE inhibitors). It may recur in subsequent pregnancies.

Fetal echo

Fetal echo (by transabdominal or transvaginal ultrasound examination) is carried out in a number of specialist centres to determine if there is a cardiac abnormality in the unborn child. Some cases have been surgically corrected in utero.

7.2 RHYTHM DISTURBANCES

Arrhythmias can be primary abnormalities or occur in association with structural heart disease. This may include congenital abnormalities or those of the myocardium, valves, pericardium or coronary arteries. The main use of echo is in determining associated heart disease.

Atrial fibrillation (AF) or flutter

Fibrillation refers to the situation when electrical activity is not coordinated in a chamber and individual muscle fibres contract independently. This can occur in atrial or ventricular muscle. Ventricular fibrillation (VF), unless promptly terminated, is fatal. AF can be tolerated, and, apart from the occurrence of atrial and ventricular extrasystoles, is the most common arrhythmia in many countries. An underlying cause for AF should always be sought.

Common causes of AF

• Ischaemic heart disease

• Rheumatic heart disease, e.g. MS

• Hypertension

• Toxins, e.g. ethanol

• Thyroid disease – usually thyrotoxicosis

• Infection – myocarditis, pneumonia

• Myocardial disease, e.g. dilated cardiomyopathy

• Lung disease

• Pulmonary embolism

• Pericardial disease, e.g. pericarditis

• ‘Lone’ – no underlying cause found.

All individuals with AF should have an echo. This is to determine an underlying cause (e.g. MS), assess the risk of complications (such as stroke, see below) and assess the likelihood of successful restoration to normal sinus rhythm (cardioversion) by electrical or chemical means.

Echo detects an underlying cardiac disorder in approximately 10% of subjects with AF who have no other clinically suspected heart disease and in 60% of those with some indicators of heart disease.

Restoration of sinus rhythm is less likely to be successful if there is:

• An enlarged LA

• LV dysfunction

• Thyroid disease

• Long-standing AF.

Unless there is a contraindication, individuals with AF have an improved prognosis if treated with anticoagulants such as warfarin. This is certainly true for rheumatic AF and probably in non-rheumatic AF where there is an underlying cause. It is less certain in ‘lone’ AF. This benefit increases with the age of the individual.

The annual risk of stroke is increased in subjects with LA enlargement or LV dysfunction:

Findings	Annual stroke risk (%)
Normal heart – sinus rhythm	0.3
‘Lone’ AF	0.5
AF with normal echo	1.5
AF with enlarged LA >2.5 cm/m²	8.8
AF with global LV dysfunction	12.6
AF with enlarged LA (>2.5 cm/m²) and moderate LV dysfunction	20.0

Data from Stroke Prevention in Atrial Fibrillation Study Group Investigators. Ann Intern Med 1992; 116:6–12.

There is evidence to suggest that, in many individuals with AF, heart rate control (e.g. with digoxin, β-blockers or calcium-channel blockers) and long-term anticoagulation with warfarin is preferable to attempting rhythm control (i.e. cardioversion). Cardioversion may be considered if:

• Recent-onset AF with an identifiable reversible cause (e.g. recent treated pneumonia)

• Subject is very symptomatic and unable to tolerate AF and/or rate-controlling medications

• AF has caused heart failure

• Individual is unable to take long-term anticoagulants.

Following successful cardioversion, warfarin should be continued for 3–6 months, since the return of atrial mechanical activity (at which time thromboembolism might occur) is often delayed, due to atrial ‘stunning’, relative to the restoration of synchronized atrial electrical activity.

In some individuals with AF, catheter ablation of the rhythm disturbance is considered.

Echo before cardioversion

This may help to identify those most likely to have successful cardioversion to sinus rhythm or to predict those at increased risk of thromboembolic complications. Previous data suggest that 5–7% of subjects undergoing cardioversion who have not been anticoagulated suffer thromboembolic complications. These may not occur until some time after cardioversion. The most likely explanation is that atrial mechanical activity may not return for some time after the restoration of atrial electrical activity.

There is some controversy regarding the use of TOE in patients with chronic AF (>48 h) prior to cardioversion. Pre- and post-cardioversion anticoagulation is indicated and large studies are underway. There is less information in recent-onset AF (<48 h) but present data suggest that 14% of patients with recent AF have LA appendage thrombus, suggesting that these patients should also be anticoagulated.

Tags: Echo Made Easy

Jun 11, 2016 | Posted by admin in CARDIOLOGY | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access