1 Cardiovascular Assessment and ECG Fundamentals

Build a focused cardiovascular assessment

A focused cardiovascular assessment brings together symptoms, vital signs, physical findings, and ECG results. No single finding—including an ECG that looks normal—should be interpreted in isolation. These adult assessment basics must be considered in light of age, baseline health, medications, and clinical context.

Ask about symptoms and history

Clarify symptom onset, location, duration, character, severity, and pattern. Ask what brings the symptom on or relieves it, whether it is changing, and whether it occurs with chest discomfort, shortness of breath, palpitations, dizziness or fainting, sweating, nausea, or unusual fatigue. Ask about relevant cardiac history, risk factors, recent illness, and medications, including recent changes.

Chest pressure or discomfort may spread to the arm, back, neck, jaw, or stomach. Heart-attack symptoms can also include shortness of breath, nausea, cold sweat, and lightheadedness; symptoms may be less typical or less obvious in some people. Treat concerning symptoms urgently rather than waiting for a classic presentation.

Observe and examine

Begin by observing alertness, color, sweating, work of breathing, and signs of distress. Examine the pulse for rate, regularity, strength, and symmetry. If the rhythm is irregular, count the pulse for a full minute and compare it with the heart rate on a monitor or ECG when available.

Measure blood pressure and repeat an unexpected reading using the correct cuff size and positioning. Consider the person’s usual readings and symptoms. Listen systematically for S₁ and S₂, extra sounds, and murmurs; a traditional sequence is the aortic, pulmonic, Erb’s point, tricuspid, then mitral (apical) areas.

Assess peripheral temperature and color, capillary refill, edema, and neck-vein distention. Assess lung sounds when breathlessness or fluid overload is suspected. Breathlessness, crackles, neck-vein distention, and peripheral edema together can suggest congestion, but require clinical evaluation. Cardiovascular examination includes inspection, palpation, and auscultation, integrated with vital signs and the person’s overall condition.

Interpret vital signs in context

For a resting adult, common reference values are a pulse of $60\text{–}100\text{ beats/min}$, respirations of $12\text{–}18\text{ breaths/min}$, and blood pressure roughly from $90/60\text{ mmHg}$ to $120/80\text{ mmHg}$. These are general reference ranges, not universal targets or proof that a person is well. Age, activity, health, and other factors affect interpretation.

Consider trends, symptoms, and the person’s baseline; repeat or escalate abnormal or concerning measurements. Record values and circumstances clearly—for example, “pulse $118$ and irregular; blood pressure $92\text{ mmHg systolic}, 58\text{ mmHg diastolic}$; reports dizziness.” A number without context can obscure clinical deterioration.

Understand what an ECG shows

An ECG records the heart’s electrical activity through skin electrodes. A standard 12-lead ECG uses $10$ electrodes to produce $12$ views of that activity; it is not the same as a continuous rhythm monitor. Correct electrode placement matters because errors can alter the tracing and its interpretation.

Before measuring, check the printed calibration and paper speed. At the standard recording speed of $25\text{ mm/s}$, one small horizontal box represents $0.04\text{ seconds}$, and one large box—five small boxes—represents $0.20\text{ seconds}$. At standard calibration, $10\text{ mm}$ vertically represents $1\text{ mV}$.

Recognize ECG waves and intervals

Each ECG feature represents a part of the heart’s electrical activity:

• P wave: atrial depolarization.

• PR interval: the time from the start of the P wave to the start of the QRS complex; commonly $0.12\text{–}0.20\text{ seconds}$ in adults.

• QRS complex: ventricular depolarization; typically less than $0.12\text{ seconds}$.

• ST segment: the period after ventricular depolarization and before the T wave. New elevation or depression may be significant in the appropriate clinical setting.

• T wave: ventricular repolarization.

• QT interval: ventricular depolarization and repolarization together. Interpretation depends on heart rate and usually uses a corrected value, QTc.

These ranges are learning guides. A clinician should interpret the full tracing, account for context, and compare with prior ECGs when possible.

Read a tracing systematically

Use a consistent sequence rather than guessing from the overall shape:

1. Check the tracing: verify patient identity, date and time, calibration, paper speed, lead quality, and possible artifact.

2. Estimate rate: for a regular rhythm, count the large boxes between consecutive R waves and divide $300$ by that number. For an irregular rhythm, count QRS complexes in a $6\text{-second}$ strip and multiply by $10$ for an approximate rate.

3. Assess regularity: compare R–R intervals; if P waves are visible, assess P–P intervals too.

4. Look for atrial activity: check whether there is a P wave before each QRS and whether the P waves look alike.

5. Check conduction: assess the PR interval and whether every P wave is followed by a QRS.

6. Assess QRS width, then ST segments and T waves. Look for new or changing abnormalities and compare them with symptoms and prior tracings.

7. Match the ECG to the person: assess pulse, blood pressure, breathing, mental status, and symptoms. Escalate concerning findings promptly.

Recognize common rhythm clues

These patterns are recognition clues, not a substitute for trained interpretation or clinical assessment:

• Sinus rhythm: regular rhythm with a consistent P wave before each QRS; the adult resting rate is commonly $60\text{–}100\text{ beats/min}$.

• Sinus bradycardia or tachycardia: a sinus-pattern rhythm below $60$ or above $100\text{ beats/min}$ in an adult. Assess symptoms and cause rather than judging the number alone.

• Atrial fibrillation: an irregularly irregular ventricular rhythm without consistent, organized P waves.

• Atrial flutter: repeating flutter-like atrial activity; the ventricular rhythm may be regular or irregular.

• Supraventricular tachycardia (SVT): often a fast, regular, narrow-complex rhythm; P waves may be difficult to see.

• Ventricular tachycardia (VT): often a fast, wide-complex rhythm; it may compromise circulation and can be life-threatening.

• Ventricular fibrillation (VF): disorganized electrical activity with no effective pulse; a cardiac-arrest emergency.

A monitor alarm or automated ECG interpretation is not a diagnosis. Confirm the person’s condition and rhythm, check for artifact, and follow local escalation procedures.

Respond to possible cardiac emergencies

Activate emergency help for severe or persistent chest discomfort, sudden breathing difficulty, fainting or new confusion, signs of poor perfusion such as marked weakness, clammy skin, or hypotension, or a new sustained rhythm abnormality—especially when symptoms or vital signs are worsening.

Acute coronary syndrome can cause chest pressure, radiating discomfort, shortness of breath, dizziness, nausea, or sweating. Diagnosis uses clinical assessment and tests such as ECG and blood tests; do not use an ECG alone to rule it out.

If someone is unresponsive and not breathing normally, treat this as possible cardiac arrest: activate emergency response, start CPR, and use an AED as soon as available, following your training and local protocol. For suspected heart-attack symptoms in the United States, call 911 rather than driving yourself.

Apply the findings together

A person reports new chest pressure and shortness of breath. Their pulse is $116$ and irregular, and blood pressure is $88\text{ mmHg systolic}, 56\text{ mmHg diastolic}$. The ECG appears irregular, but the immediate priority is not to name the rhythm: the symptoms and low blood pressure suggest possible instability. Activate the appropriate emergency response, assess the person continuously, and obtain urgent clinical evaluation.

This example shows why symptoms, perfusion, vital signs, and ECG findings must be considered together.