Module 3
Module 3: Cardiovascular & Respiratory
Evaluate heart murmurs, recognize respiratory distress, and assess cyanosis
Welcome to Module 3!
In this module, you’ll develop critical skills in cardiovascular and respiratory assessment. Heart murmurs are common in newborns, but distinguishing innocent from pathological murmurs is essential for appropriate management. You’ll also learn to recognize respiratory distress patterns and evaluate cyanosis—key findings that require rapid assessment and intervention.
Learning Objectives
By the end of this module, you will be able to:
- ✅ Perform systematic cardiac auscultation in newborns
- ✅ Characterize murmurs and determine need for echocardiography
- ✅ Differentiate innocent murmurs from pathological cardiac disease
- ✅ Recognize signs and severity of respiratory distress
- ✅ Differentiate central from peripheral cyanosis
- ✅ Develop differential diagnosis for cardiorespiratory findings
- ✅ Know when urgent cardiology or critical care consultation is needed
Lesson 1: Cardiac Auscultation and Heart Murmurs
Anatomy Review
The newborn heart is functionally different from the adult heart due to fetal adaptations that are gradually disappearing:
Fetal Shunts Being Closed:
- Patent Foramen Ovale (PFO): Normal patent opening between right and left atria, allows right-to-left shunting during fetal life
- Patent Ductus Arteriosus (PDA): Normal connection between pulmonary artery and aorta, allows right-to-left shunting in utero
- Fetal Blood Vessel: Ductus venosus (shunts umbilical blood away from liver)
Timeline for Closure:
- Ductus venosus: Functionally closes within hours
- Foramen ovale: Usually functionally closes within hours to days (anatomically may remain probe-patent)
- Ductus arteriosus: Functionally closes by 24-72 hours, but full closure takes weeks
This transitional period explains why innocent murmurs are very common in the first days of life.
Cardiac Examination Technique
Positioning:
- Examine infant when calm and quiet (not crying)
- Inspect anterior chest wall for scars, precordial bulging
- Note any visible pulsations (hyperdynamic circulation vs normal)
Palpation:
- Locate the apical impulse (should be at 4th-5th intercostal space, midclavicular line)
- Assess for thrills (palpable vibrations indicating significant murmur)
- Note if apical impulse is hyperkinetic (strong, bounding) or weak
- Assess brachial and femoral pulses simultaneously for timing (should be equal)
Auscultation:
- Use both diaphragm and bell of stethoscope
- Examine systematically: apex, left lower sternal border, left upper sternal border, right upper sternal border
- Listen for each of the four main heart sounds:
- S1 (lub): Closure of atrioventricular valves (mitral + tricuspid)
- S2 (dub): Closure of semilunar valves (aortic + pulmonary)
- S3 (often heard as third sound after S2): Ventricular filling sound - normal in infants
- S4: Atrial kick - less common in newborns unless pathological
Listening for Murmurs:
- Note timing: Systolic (between S1 and S2), diastolic (between S2 and next S1), or continuous
- Note location and radiation
- Note quality: Musical, blowing, harsh, vibratory
- Note intensity: Grade 1-6 (see below)
- Note changes with position, crying, or activity
Murmur Grading System
| Grade | Description | Clinical Significance |
|---|---|---|
| 1/6 | Barely audible, requires careful listening | Usually innocent |
| 2/6 | Quiet but easily heard | Usually innocent |
| 3/6 | Moderate intensity, clearly audible | May be innocent or pathological |
| 4/6 | Loud, associated with a thrill | Suggests significant pathology |
| 5/6 | Very loud with thrill, heard with stethoscope off chest | Significant pathology likely |
| 6/6 | Heard without stethoscope (extremely rare) | Severe pathology |
Clinical Pearl: Murmur intensity does NOT always correlate with severity of disease. Some innocent murmurs can be quite loud, while some serious heart lesions may produce only soft murmurs.
Red Flags in Cardiac Examination
Findings that require urgent cardiology evaluation:
- Thrill on palpation - indicates significant murmur
- Grade 4-6 murmurs - especially if systolic
- Cyanosis - central cyanosis with murmur suggests critical cardiac disease
- Signs of heart failure: Hepatomegaly, tachypnea, poor feeding, failure to thrive
- Bounding pulses with wide pulse pressure - suggests PDA or other left-to-right shunt
- Absent or diminished femoral pulses - concerns for coarctation of aorta
- Sustained tachycardia or bradycardia
- Arrhythmias
Lesson 2: Innocent vs Pathological Murmurs
Innocent Murmurs of the Newborn
The most common heart finding in newborns is an innocent murmur. It’s estimated that 50-90% of healthy newborns have a murmur during the first week of life, primarily due to transitional circulation changes.
PDA Murmur (Patent Ductus Arteriosus)
When present in first days of life, very common and usually transitions to closure naturally.
Characteristics of PDA Murmur:
- Timing: Continuous (heard throughout systole and into diastole) - the classic “machinery” murmur
- Location: Left infraclavicular area, left sternal border
- Quality: Machinery-like, whooshing sound
- Associated findings:
- Bounding pulses (hyperdynamic pulses)
- Wide pulse pressure (difference between systolic and diastolic)
- Hyperactive precordium
- Possible hepatomegaly (only if hemodynamically significant)
Course in Newborn:
- Many close naturally by 24-48 hours
- May persist longer in preterm infants
- Small PDAs are clinically insignificant
- Hemodynamically significant PDA (causing pulmonary edema, poor feeding) requires treatment (indomethacin, ibuprofen, or surgical ligation)
When to Worry:
- Signs of pulmonary edema (tachypnea, crackles)
- Feeding difficulty or poor weight gain
- Severe left-to-right shunt physiology
- Prematurity (higher risk of hemodynamically significant PDA)
Transitional Murmurs
Pulmonary/Tricuspid Flow Murmur:
- Timing: Systolic (early-to-mid or holodiastolic)
- Location: Left sternal border, 2nd-3rd intercostal space
- Cause: Increased flow across pulmonary valve due to closing of ductal shunt
- Course: Resolves as fetal shunts fully close (usually by 48 hours)
- Characteristics: Grade 1-2, soft, no associated thrills
- Associated findings: Normal bounding pulses, no cyanosis, no hepatomegaly
Vibratory Murmur (Still’s Murmur):
- Timing: Early-to-mid systolic
- Location: Left sternal border, 3rd-4th intercostal space
- Characteristics: Grade 1-3, vibratory or musical quality (sometimes sounds like a plucked string)
- Unique feature: Decreases with upright position or during crying
- Significance: Completely benign, often heard in healthy children; disappears within days to weeks
- No associated findings: Normal S2, normal pulses, no cyanosis
Aortic Stenosis Murmur (Mild):
- Timing: Systolic ejection type
- Location: Right sternal border, radiates to neck
- Characteristics: Grade 1-2, no thrill
- Associated findings: Normal femoral pulses, normal blood pressure in all extremities
- Key feature: No evidence of left ventricular hypertrophy or strain
Characteristics of Innocent Murmurs
Innocent murmurs typically have these features:
- No cyanosis - baby appears pink, oxygen saturation normal
- No signs of heart failure - feeding well, appropriate growth, no respiratory distress
- Normal S2 - split appropriately with breathing (widens on inspiration, narrows on expiration)
- No thrill - palpable vibrations absent
- Grade 1-2/6 - soft, or at most grade 3/6 with musical quality
- Systolic timing - murmurs that are diastolic are always concerning
- Normal pulses - brachial and femoral pulses equal and normal
- Normal blood pressure in all extremities - no differential BP between arms and legs
- No hepatomegaly - liver edge at normal position
- Normal first 24-48 hours - many resolve spontaneously
Pathological Murmurs Requiring Workup
Red Flags that Indicate Need for Further Evaluation:
- Diastolic murmurs - almost always abnormal in newborns
- Grade 4-6 systolic murmur - especially with associated thrill
- Cyanosis - always a concern requiring urgent evaluation
- Signs of heart failure: Tachypnea >60, hepatomegaly, feeding difficulty
- Abnormal S2 - single S2 or abnormal splitting pattern
- Arrhythmias - irregular heart rate requires ECG
- Differential blood pressures - coarctation concern if femoral pulses weak
- Weak or absent pulses - critical cardiac disease or shock
Common Congenital Heart Lesions
Presenting with Murmurs:
| Lesion | Timing | Location | Key Features | Urgency |
|---|---|---|---|---|
| Ventricular Septal Defect (VSD) | Holosystolic | Left sternal border, 4th ICS | Harsh, thrill common, possible pulmonary ejection sound | Depends on size |
| Atrial Septal Defect (ASD) | Systolic ejection, diastolic | Right upper sternal | Fixed split S2, may have diastolic rumble | Low unless severe |
| Patent Ductus Arteriosus (Significant) | Continuous “machinery” | Left infraclavicular | Bounding pulses, wide pulse pressure, signs of pulmonary edema | Moderate |
| Coarctation of Aorta | Systolic | Left sternal border, back | Weak/absent femoral pulses, BP higher in arms than legs | Urgent |
| Tetralogy of Fallot | Systolic | Left sternal border | Cyanosis, single loud S2, “boot-shaped” heart on CXR | Urgent |
| Transposition of Great Arteries | Minimal murmur common | - | Severe cyanosis with minimal murmur, egg-on-string appearance | EMERGENCY |
Critical Note: Some life-threatening cardiac lesions have minimal or NO murmur (e.g., critical aortic stenosis, hypoplastic left heart syndrome, transposition). Never rely on presence or absence of murmur alone.
Echocardiography Indications
Echocardiography is indicated for:
- Any diastolic murmur
- Systolic murmur with thrill
- Murmur grade 4/6 or greater
- Murmur associated with:
- Cyanosis
- Signs of heart failure
- Differential blood pressures
- Abnormal femoral pulses
- Abnormal S2 or arrhythmia
- Failure to thrive or poor feeding
- High risk for CHD (maternal diabetes, congenital infection, syndromic features)
- Asymptomatic but murmur persists beyond first week
Observation Alone is Acceptable for:
- Typical innocent murmur (vibratory, soft, systolic)
- Normal associated findings
- Parents can return for follow-up examination
Lesson 3: Respiratory Examination in Newborns
Normal Newborn Breathing Patterns
Normal Respiratory Rate:
- Term newborn: 30-60 breaths per minute
- Count for full minute if possible
- Rate varies with state (sleep, awake, crying)
Normal Breathing Pattern:
- Quiet, effortless respirations
- Periodic breathing: Brief apneic pauses (up to 10 seconds) followed by rapid breathing - normal in newborns
- Symmetrical chest wall movement
- No audible sounds
Characteristics of Healthy Respiration:
- No grunting
- No retractions
- No nasal flaring
- No cyanosis
- Normal oxygen saturation (≥95% on room air after first few hours)
Work of Breathing Assessment
The key to recognizing respiratory distress is assessing WORK of breathing, not just rate.
Physical Signs of Increased Work of Breathing:
| Finding | Location | Significance |
|---|---|---|
| Intercostal retractions | Between ribs | Negative intrathoracic pressure needed to pull in ribs |
| Subcostal retractions | Below lower chest | Increased respiratory effort |
| Suprasternal retractions | Above clavicles, base of neck | Significant respiratory distress |
| Nasal flaring | Nostrils | Accessory muscle use |
| Grunting | End-expiratory sound | Infant trying to maintain positive end-expiratory pressure |
| Head bobbing | Neck with each breath | Use of neck muscles as accessory muscles |
| Cyanosis | Lips, tongue, mucous membranes | Central cyanosis - hypoxia |
Respiratory Distress Severity
Silverman Score (useful tool to quantify severity): Scores 0-10 (higher = more distress)
| Finding | Score 0 | Score 1 | Score 2 |
|---|---|---|---|
| Chest wall movement | Synchronized | Lag on inspiration | See-saw |
| Intercostal retractions | None | Minimal | Marked |
| Xiphoid retractions | None | Minimal | Marked |
| Nasal flaring | None | Minimal | Marked |
| Grunting | None | On stethoscope | Audible without scope |
Clinical Interpretation:
- 0-3: Mild, may self-resolve with support
- 4-6: Moderate, likely needs oxygen and monitoring
- 7-10: Severe, needs critical care intervention
Common Causes of Respiratory Distress
Pulmonary Causes (most common):
- Respiratory Distress Syndrome (RDS): Surfactant deficiency in preterm infants - presents with tachypnea, retractions, grunting, cyanosis within 1-2 hours of birth
- Meconium Aspiration Syndrome (MAS): Aspiration of meconium-stained amniotic fluid - presents with tachypnea, hyperinflation on CXR
- Transient Tachypnea of Newborn (TTN): “Wet lung,” delayed clearance of fetal lung fluid - common in term infants born via C-section, resolves over 24-72 hours
- Pneumonia: Perinatal infection - presents with tachypnea, may have maternal risk factors (fever, prolonged ROM, chorioamnionitis)
- Aspiration: Feeding-related or amniotic fluid - risk of chemical pneumonitis
- Pneumothorax: Spontaneous or from positive pressure ventilation - presents suddenly with acute deterioration, unilateral decreased breath sounds
Cardiac Causes:
- Pulmonary edema: From left heart failure, significant PDA, or other cardiac pathology - wet crackles on exam, fluid on CXR
- Critical cardiac disease: Transposition, HLHS, etc.
Other Causes:
- Infection/Sepsis: Bacterial or viral pneumonia, includes systemic signs
- Metabolic: Severe metabolic acidosis can cause Kussmaul breathing
- Neurological: Poor respiratory drive from perinatal HIE, birth trauma, or drugs
- Airway: Choanal atresia, micrognathia, tracheomalacia
- Abdominal: Diaphragmatic hernia, abdominal wall defect (increases intra-abdominal pressure)
Examination of Lungs
Inspection:
- Symmetry of chest wall movement
- Presence of retractions, flaring, grunting
- Skin color for cyanosis
- Respiratory rate and pattern
Auscultation:
- Listen to bilateral anterior and posterior chest
- Assess air entry: Should be equal and present bilaterally
- Listen for adventitious sounds:
- Crackles (rales): Fine, wet sounds - suggests pulmonary edema or pneumonia
- Wheezes: Higher-pitched, musical - suggests air trapping or bronchospasm
- Grunting: Low-pitched sound at end of expiration - compensatory mechanism
- Stridor: High-pitched sound on inspiration - upper airway obstruction
Palpation:
- Assess chest wall tenderness or crepitus
- Check for subcutaneous emphysema (air in subcutaneous tissues)
Lesson 4: Cyanosis Evaluation
Definition and Pathophysiology
Cyanosis is a blue-purple discoloration of skin and mucous membranes caused by increased deoxygenated hemoglobin (>5 g/dL).
Important Clinical Note: Cyanosis is a SIGN, not a diagnosis. Your job is to determine the cause.
Central vs Peripheral Cyanosis
Central Cyanosis:
- Affects lips, tongue, mucous membranes, trunk
- Always abnormal - indicates low oxygen saturation in arterial blood
- Suggests inadequate oxygenation in lungs or mixing of deoxygenated blood
Peripheral Cyanosis:
- Affects hands, feet, areas of vasoconstriction
- May be normal in newborns due to slow peripheral circulation
- Seen with cold exposure, peripheral vasoconstriction, or poor perfusion
- Benign if: Central areas pink, oxygen saturation normal, no other signs of distress
Quick Differentiation:
- Check mucous membranes (inside lip): If blue = CENTRAL CYANOSIS (concerning)
- Check trunk, axillae: If blue = CENTRAL CYANOSIS (concerning)
- Check only hands/feet: Likely PERIPHERAL CYANOSIS (benign if well perfused)
Central Cyanosis - Differential Diagnosis
Central cyanosis in newborns = emergency requiring rapid evaluation
Pulmonary Causes (most common):
- Respiratory distress syndrome (preterm infants)
- Meconium aspiration syndrome
- Transient tachypnea of newborn
- Pneumonia (congenital or acquired)
- Pulmonary hypoplasia (associated with oligohydramnios)
- Persistent pulmonary hypertension of newborn (PPHN)
Cardiac Causes (critical - requires immediate intervention):
- Transposition of Great Arteries (TGA): Most common cyanotic lesion in newborns - minimal murmur, severe cyanosis, “egg-on-string” appearance on CXR
- Tetralogy of Fallot (TOF): Clubbing develops later; systolic murmur; “boot-shaped” heart on CXR
- Critical Pulmonary Stenosis/Atresia: Right-to-left shunt
- Tricuspid Atresia: Requires PDA for survival
- Total Anomalous Pulmonary Venous Return (TAPVR): Subtle findings, may have murmur
- Hypoplastic Left Heart Syndrome: PDA-dependent lesion, severe distress
- Ebstein’s Anomaly: Variable presentation
Hematologic/Metabolic Causes (less common):
- Severe anemia (though typically presents with pallor, not cyanosis)
- Polycythemia (can have sluggish circulation)
- Methemoglobinemia (dark cyanosis, unresponsive to oxygen)
Hyperoxia Test
Used to differentiate pulmonary from cardiac causes of cyanosis.
Procedure:
- Document baseline oxygen saturation in room air
- Place infant in 100% oxygen for 10 minutes (via hood or nasal cannula, not bag-mask)
- Obtain arterial blood gas or recheck oxygen saturation
- Observe for improvement in cyanosis
Interpretation:
| Result | Meaning | Examples |
|---|---|---|
| SpO2 increases to >95% or PaO2 >100 mmHg | PULMONARY cause likely | RDS, TTN, aspiration, infection |
| SpO2 remains <80% or PaO2 <50 mmHg | CARDIAC cause likely (right-to-left shunt) | TGA, TOF, critical stenosis |
| Borderline response | Severe pulmonary disease OR complex cardiac disease | PPHN, severe pneumonia, mixed lesions |
Clinical Pearl: A NEGATIVE hyperoxia test (cyanosis that doesn’t improve with oxygen) is strongly suggestive of congenital heart disease requiring immediate cardiology consultation.
Red Flags Requiring Urgent Evaluation
EMERGENCY - Seek immediate critical care consultation for:
- Central cyanosis (any severity)
- Cyanosis + any murmur
- Cyanosis + respiratory distress
- Cyanosis + poor feeding
- Cyanosis + poor perfusion, weak pulses
- Cyanosis + shock signs (altered mental status, mottled skin, hypotension)
Critical Actions:
- Get oxygen on: Start supplemental oxygen immediately
- Get a helper: Call for nursing support and attending
- Establish IV access: May need fluids or medications
- Monitor continuously: Pulse oximetry, cardiac monitoring, vital signs
- Get imaging: Chest X-ray immediately, consider echocardiography
- Prepare for intervention: Some lesions need PDA kept open (prostaglandin E1), some need emergency repair
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Exercise 3.1: Heart Murmurs - Identification and Significance
Practice differentiating innocent from pathological murmurs and determining appropriate diagnostic workup.
Exercise 3.1: Heart Murmurs - Identification and Significance
Your Challenge
Review clinical scenarios describing newborns with murmurs. For each case, characterize the murmur, assess likelihood of innocent versus pathological findings, identify any concerning associated features, and recommend appropriate diagnostic steps.
📋 View Clinical Cases with Murmurs
Exercise 3.2: Respiratory Patterns and Distress Recognition
Develop skills in recognizing normal breathing patterns and identifying respiratory distress in newborns.
Exercise 3.2: Respiratory Patterns and Findings
Your Challenge
Review clinical scenarios and descriptions of newborns with different respiratory patterns. Assess respiratory rate, work of breathing, identify signs of distress, suggest differential diagnoses, and determine urgency of intervention.
📋 View Respiratory Cases
Exercise 3.3: Cyanosis Evaluation
Master the systematic evaluation of cyanosis and differentiation between benign and pathological causes.
Exercise 3.3: Cyanosis Evaluation
Your Challenge
Evaluate cases with cyanosis. Differentiate central from peripheral cyanosis, develop comprehensive differential diagnoses, recommend appropriate diagnostic workup including hyperoxia testing, and determine urgency of intervention.
📋 View Cyanosis Cases
Module 3 Complete!
Congratulations on completing Module 3! You’ve developed essential skills in cardiovascular and respiratory assessment:
✅ Systematic cardiac auscultation techniques ✅ Characterization of murmurs and differentiation of innocent from pathological findings ✅ Understanding of transitional circulation and its clinical significance ✅ Recognition of respiratory distress and work of breathing assessment ✅ Comprehensive cyanosis evaluation and emergency recognition ✅ Knowledge of when urgent specialist consultation is needed
Key Takeaways
-
Murmurs are Common - Up to 90% of newborns have a murmur in the first week due to transitional circulation. Most resolve spontaneously.
-
Innocent vs Pathological - Innocent murmurs are soft (grades 1-2), systolic, vibratory or musical, with no associated signs of cardiac disease. Always get an echo if unsure.
-
Red Flags - Diastolic murmurs, thrills, cyanosis, signs of heart failure, abnormal pulses or S2, and arrhythmias all warrant further evaluation.
-
Assess Work of Breathing, Not Just Rate - Retractions, grunting, flaring, and use of accessory muscles indicate respiratory distress more than rate alone.
-
Central Cyanosis is an Emergency - Any infant with central cyanosis (blue lips/tongue/mucous membranes) needs immediate evaluation. Hyperoxia testing helps differentiate pulmonary from cardiac causes.
-
Critical Cardiac Lesions May Have No Murmur - Never rely on presence or absence of murmur alone. Some dangerous lesions (transposition, critical aortic stenosis, hypoplastic left heart) have minimal or no murmur.
-
PDA is Transitional - Many PDAs close spontaneously in the first 24-48 hours. Only hemodynamically significant ones require treatment.
-
Differential Diagnosis Matters - Consider the clinical context (prematurity, labor complications, maternal factors) when developing your differential.
Safety Points to Remember
EMERGENCIES - Seek immediate critical care:
- Central cyanosis of any severity
- Severe respiratory distress (Silverman score >7)
- Ductus-dependent critical cardiac lesions (signs of shock developing as PDA closes)
- Severe pulmonary hypertension (right-to-left shunting)
URGENT - Obtain evaluation within hours:
- Murmurs with associated signs (hepatomegaly, abnormal pulses, failure to thrive)
- Moderate respiratory distress
- Persistent tachycardia or bradycardia
ROUTINE - Can be evaluated outpatient if stable:
- Innocent murmurs with no concerning features
- Mild, transient tachypnea resolving
- Peripheral cyanosis that clears with warming
What’s Next?
In Module 4, you’ll learn abdominal, genitourinary, and musculoskeletal examination skills. You’ll practice identifying common findings like umbilical hernias, assessing the hip examination for developmental dysplasia, and recognizing musculoskeletal variations.