Assessment of fetal heart function and rhythm

Transcription

1 Assessment of fetal heart function and rhythm

2 The fetal myocardium Early Gestation Myofibrils 30% of myocytes Less sarcoplasmic reticula Late Gestation Myofibrils 60% of myocytes Increased force per unit area Improved relaxation / contractile ability Active tension Passive tension

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4 Gestational changes Systolic period stays the same Diastolic period gets longer longer early filling and atrial contraction periods Shorter isovolumic relaxation LV and RV systolic and diastolic BP increase No difference between LV and RV in paired samples Atrial pressures don t change with gestation LA mean 3.3mmHg, RA mean 3.6mmHg

5 The fetal circulation Oxygenated blood from placenta streams to left heart High pulmonary vascular resistance Low resistance placental circulation Cerebrovascular resistance is autoregulatory

6 Advantage of fetal circulation Parallel rather than series, with (at least) two options for shunting If one ventricle fails, re-distribution of blood to the other ventricle is possible in most cases This leads to the one good inlet, one good outlet rule Dysfunction usually only results in poor outcome ( fetal heart failure ) when central venous pressure is elevated

7 Assessment of fetal cardiac function AHA Guidelines Routine Heart size and thickness CTR and qualitative Systolic Diastolic Specific * Qualitative Myocardiac performance (Tei) index Cardiac output Specialized / research Tissue Doppler Strain Doppler assessment

8 Cardiothoracic circumference ratio = Cardiothoracic area ratio = Cardiothoracic ratio

9 Systolic function Mainly qualitative Shortening fraction (2D or M-mode) = (end-diastolic end-systolic ventricular diameter) end-diastolic dimension Cardiac output

10 Combined cardiac output both ventricles contribute to systemic perfusion CSA x VTI x HR Accuracy: Axial plane PV and AoV diameters Axial plane PV and AoV VTI (small angle of insonation) Used for: High cardiac output states (anemia, teratoma, AV malformations) Low output states (e.g. Heart block, Cardiomyopathy, Ebstein s) Cardiac Output

11 Routine usage of Doppler Assess venous flow Ventricular inflows, Hepatic vein, Ductus venosus, UV Assess outflow gradients Assess MCA and UA PI

12 Ventricular inflow Passive (early) and active (late) filling properties of the ventricle A-wave dominant in fetal, becomes more even in later gestation Abnormal compliance leads to increased A- dominance.

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15 Hepatic vein Doppler Better alignment than IVC, and same waveform unless AV malformation Increased a-wave suggestive of high right atrial pressure low ventricular compliance atrial contraction against closed AV valve in arrhythmia Decreased s-wave suggestive of severe TR

16 Ductus Venosus Follow the UV, look for aliasing Saggital view is best for Doppler Normal flow is antegrade throughout cycle A-wave reversal can be an indicator of placental dysfunction / hypoxia in IUGR babies In CHD with expected high RA pressure, A-wave reversal is expected and not associated with poor outcomes (e.g. Tricuspid atresia, Pulmonary atresia)

17 Should be sampled in free loop, as can vary close to fetus or placenta Umbilical vein flow should be nonpulsatile, velocity between 10 and 20cm/s UV pulsations usually indicate severely decreased ventricular compliance Umbilical artery PI decreases with gestation Elevated UA PI indicates Increased placental resistance Steal (e.g severe pulmonary regurgitation, large AVM, vein of Galen) Umbilical vein and artery

18 Flow to brain under autoregulation Low MCA PI = reduced resistance to flow brain sparing. Suggests reduced total flow AND / OR oxygen content in blood Necessitates reduced resistance to maintain nutrient delivery. High MCA PI = brain protection from elevated flow Middle Cerebral Artery

19 Cardiovascular Profile Score

20 Types of dysfunction High Cardiac Output Causes Arteriovenous malformations Sacrococcygeal teratomas Fetal anemia Echo Findings Cardiomegaly Dilated RV / LV High cardiac output (greater than 625ml/m2 predicts risk of fetal death). IVC Sacrococcygeal teratoma

21 Types of dysfunction High afterload LVOT Doppler (normal <1m/s) Causes Aortic stenosis (LV) Twin-twin transfusion (RV > LV) Pulmonary stenosis; Ductal constriction (RV) Echo findings Reduced systolic function Reduced inflow time Endocardial fibroelastosis Abnormal venous Dopplers if both ventricles affected MV inflow

22 High afterload Aortic stenosis Selective IUGR, pulmonary stenosis

23 Types of dysfunction intrinsic contractile Cardiomyopathy: 2.5% of fetal heart disease 1/3 Hypertrophic 2/3 Dilated Echocardiographic Findings HCM Myocardial thickness > 2 z-scores above mean Normal RV / LV diameters Cardiomegaly DCM Decreased shortening fraction Predictors of poor outcome Uniphasic ventricular inflow Pulsatile UV flow Fetal hydrops

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26 Tei index = Isovolumic time Ejection time = b a a = 0.70 (NR <0.45) a b

27 Cardiovascular profile score: No hydrops = 0 UV pulsations = -2 CTR = 0.42 ( ) = -1 FS = / MR = -2 Total =5 Combined cardiac output = 192ml/min Tei = 0.70 Hepatic vein Ductus venosus UV

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29 Cardiovascular profile score No hydrops = 0 UV pulsations = 0 CTR = 0.42 ( ) = -1 FS = / MR = -2 Total =7 Combined cardiac output = 240ml/min (50 th %) RV Tei = 0.8, LV Tei 0.36

30 Another cardiomyopathy 26 weeks Family history of cardiomyopathy Non-compaction Normal inflows No venous Doppler abnormalities

31 Congenital heart disease

32 Types of dysfunction dyssynchrony Ebstein s Anomaly Atrialized right ventricle Volume loading of right (TR) Aneurysms

33 Newer measures of cardiac function Tissue velocity imaging (TVI) color or pulse wave High frame rates Simultaneous velocity measurement in multiple walls Angle dependent Strain imaging Need high frame rates

34 Fetal arrhythmia

35 Fetal Arrhythmias: Background Incidence Effects 2% of the pregnancies Accounts for 10-20% of referrals for fetal echo Risk factors Assessment Rhythm (irregular vs regular) Rate (fast vs slow University of Alberta Fetal and Neonatal Cardiology Program

36 Fetal Arrhythmia: Types Ectopy Premature atrial contractions (PAC) Junctional ectopic beats Premature ventricular contractions (PVC) Tachycardia Sinus tachycardia (HR bpm) Supraventricular (ectopic atrial tachycardia, AV reentry tachycardia and permanent junctional reciprocating tachycardia) Atrial Flutter (HR bpm due to AV block) Junctional ectopic tachycardia Ventricular tachycardia Bradycardia Sinus bradycardia (HR bpm) Premature atrial beats with AV block Difficult to differentiate Difficult to differentiate Congenital heart block (1 st not associated with bradycardia, 2 nd and 3 rd degree) University of Alberta Fetal and Neonatal Cardiology Program

37 Fetal Tachycardias: Risk factors Usually no identified risk factors Maternal conditions Maternal Beta-stimulation Thyroid-stimulating antibodies Fetal conditions Severe RA enlargement Ebstein s anomaly, tricuspid dysplasia, RA aneurysm Cardiac tumors University of Alberta Fetal and Neonatal Cardiology Program

38 Fetal Bradycardias: Risk Factors Maternal conditions: Auto-immune antibodies (Lupus, Sjogren s) 1 st, 2 nd, CHB. Exposure to medication (i.e. beta-blocker) Fetal conditions: Long QT syndrome Left atrial isomerism Fetal L-TGA sinus bradycardia / torsades sinus bradycardia / complete block complete heart block University of Alberta Fetal and Neonatal Cardiology Program

39 Fetal Arrhythmias: Making a Diagnosis Fetal echocardiogram-inferences based on mechanical atrial and ventricular events Blood-flow PW Doppler LV inflow-outflow PW Doppler SVC-Ao flow PW Doppler pulmonary branch artery-vein Muscular movement M-mode (cursor through the atrium and ventricle) Tissue Doppler Imaging Fetal ECG Fetal magnetocardiogram University of Alberta Fetal and Neonatal Cardiology Program

40 Fetal Arrhythmias: Making a Diagnosis M-mode: Left atrium - right ventricle PW Doppler: SVC - Ao flow V V V V V V A A A A A A PW Doppler: LV inflow/outflow PW Doppler: pulmonary vein/artery inflow PA flow outflow University of Alberta Fetal and Neonatal Cardiology Program Pulm vein flow

41 Fetal Arrhythmias: Making a Diagnosis Mechanical PR interval PW Doppler: SVC AO PW Doppler: LV inflow/outflow SVC Ao A A V A V V University of Alberta Fetal and Neonatal Cardiology Program

42 Fetal Arrhythmias: Types Ectopy Premature atrial contractions (PAC) Junctional ectopic beats Premature ventricular contractions (PVC) Tachycardia Sinus tachycardia (HR bpm) Supraventricular (EAT, AVRT and PJRT) Atrial Flutter (HR bpm) Junctional ectopic tachycardia Difficult to differentiate Ventricular tachycardia Bradycardia Sinus bradycardia (HR bpm) Premature atrial beats with AV block Congenital heart block (1 st, 2 nd and complete) Difficult to differentiate University of Alberta Fetal and Neonatal Cardiology Program

43 Fetal Arrhythmias: Ectopy Premature atrial contractions (PAC) Incidence: 5% of all pregnancies >30 weeks Benign in 98%; ~ 2% will trigger/be associated with intermittent SVT or atrial flutter Associated with CHD in 1-10% cases University of Alberta Fetal and Neonatal Cardiology Program

44 Conducted PACs Fetal Ectopy: PACs V V V V V V V V A PAC A PAC A PAC A PAC V Blocked PACs V A PAC A PAC University of Alberta Fetal and Neonatal Cardiology Program

45 Fetal Ectopy: PVCs Premature ventricular contractions (PVC) PVCs are 10x less common than PACs PVCs can be associated with VT Difficult to differentiate from junctional ectopic beats without an ECG Associated with cardiomyopathies myocarditis intracardiac tumors University of Alberta Fetal and Neonatal Cardiology Program

46 Fetal Ectopy: PVCs 2X V V V V V V X A A A A A A X University of Alberta Fetal and Neonatal Cardiology Program

47 Fetal Arrhythmias: Types Tachycardia Sinus tachycardia (HR bpm) Supraventricular (SVT) Ectopic atrial tachycardia (EAT) Atrioventricular re-entry tachycardia (AVRT) Permanent junctional re-entry tachycardia (PJRT) Atrial Flutter (HR bpm) Junctional ectopic tachycardia Ventricular tachycardia Bradycardia Sinus bradycardia (HR bpm) Premature atrial beats with AV block Congenital heart block (1 st, 2 nd and complete) Difficult to differentiate Difficult to differentiate University of Alberta Fetal and Neonatal Cardiology Program

48 Fetal Tachycardias: SVT SVT Most common fetal tachycardia (66-90%) Usually 1:1 A-V conduction Includes: AVRT, EAT and PJRT Nonimmune hydrops in 40-50% (older series) and 20-25% (recent series) which increases risk of fetal and neonatal demise even with treatment (with successful treatement <10%) Hydrops is associated with slower response to therapy and need for more than 1 medication Hydropic mechanism: ventricular compliance of the fetus filling time atrial and ventricular filling pressures pressure through the venous system University of Alberta Fetal and Neonatal Cardiology Program transudative forces cell and tissue edema

49 250 ms V V V V V A A A A A

50 Fetal Tachycardias: SVT LV inflow/outflow Short AV-long VA relationship = EAT SVC-AO flow Long AV-short VA relationship= AVRT short AV interval (75ms) Long AV interval (133ms) University of Alberta Fetal and Neonatal Cardiology Program

51 Fetal Tachycardias: Atrial Flutter Atrial flutter 20-25% of fetal tachycardias Rate~ bpm AV conduction (2:1; 3:1) > 27 weeks Hydrops ~13% University of Alberta Fetal and Neonatal Cardiology Program

52 Fetal Tachycardias: V Tachycardia/JET Rare HR ranges between bpm Intermittent runs Complete A-V dissociation Exception: retrograde conduction through the AV node = 1:1 conduction Associated with long QT syndrome suspect if intermittently bradycardic University of Alberta Fetal and Neonatal Cardiology Program

53 Fetal Tachycardias: V Tachycardia/JET o AV dissociation o Ventricular rate~ 210 bpm o 1:1 conduction o Rate bpm A A A A A A V V V V V V V University of Alberta Fetal and Neonatal Cardiology Program

54 Fetal Arrhythmias:Types Ectopy Premature atrial contractions (PAC) Junctional ectopic beats Premature ventricular contractions (PVC) Tachycardia Sinus tachycardia (HR bpm) Supraventricular (EAT, AVRT and PJRT) Atrial Flutter (HR bpm) Junctional ectopic tachycardia Ventricular tachycardia Bradycardia Sinus bradycardia (HR bpm) Premature atrial beats with AV block Congenital heart block (1 st, 2 nd and complete) Difficult to differentiate Difficult to differentiate University of Alberta Fetal and Neonatal Cardiology Program

55 Fetal Bradycardias Sinus bradycardia 1:1 AV conduction If transient, is benign Persistently low HR: Blocked PACs - common! Fetal distress usually gradual Long QT syndrome Structural CHD Left atrial isomerism L-TGA A V V A V V A A University of Alberta Fetal and Neonatal Cardiology Program

56 Fetal Bradycardias: AV Block 1 0 AVB olong A-V interval 2 0 AVB; Mobitz I oa-v interval progressively increases, then drops conduction University of Alberta Fetal and Neonatal Cardiology Program

57 Fetal Bradycardias: AV Block 2 0 AVB; Mobitz I oa-a interval regular oa-v dissociation Complete AVB oa-v dissociation oventricular rate:60-70 bpm o47% structural CHD o47% maternal antibodies University of Alberta Fetal and Neonatal Cardiology Program

58 Questions?