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Heart Rate and Pulse

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Auscultation of the Heart

 

The stethoscope is placed on the left chest and one listens to the rate, rhythm (regular, irregular) and for abnormal heart sounds (extra sounds, murmurs). In the obese male, heart sounds are best heard with the diaphragm on the left pectoralis major muscle or on the sternal borders at the left or right 2nd interspaces. In the adult female, auscultation is performed by lifting the breast and placing the stethoscope on the chest wall, or placing the diaphragm on the pectoralis major, as in the obese male. The heartbeat is best heard in the quietly supine patient.

The heart rate is referred to as the apical rate. Do not auscultate the heart over clothing. Rates are classified as normal (normal sinus rhythm, NSR), fast (tachycardia- 100 or more) or slow (bradycardia—60 or less). A normal sinus rhythm means that the beat originates in the SA node, the pacemaker. Not all bradycardias or tachycardias are abnormal. Some athletes may have normal rates of 50 or less. Anxiety may increase the rate to 120.

Rhythms are classified as regular or irregular (arrhythmias, dysrhythmias). Irregular rhythms are further categorized as regularly irregular (constant regular abnormal beats), such as seen with some premature atrial and ventricular contractions, or irregularly irregular (random irregularity), such as seen with atrial fibrillation and premature ventricular contractions. Combinations of abnormal rates and rhythms frequently exist, such as a bradycardia and an arrhythmia (bradyarrhythmia) or a tachycardia and an arrhythmia (tachyarrhythmia).

Common Fast Rates (Tachycardias)

Sinus tachycardia is a common fast rate of 100-180, originating in the SA node. It is seen during stress, anxiety, pain, and when increased circulatory demands require increased cardiac output, as in shock, congestive heart failure and fever. It is also seen in disease processes such as thyroid storm, adrenal crisis, DKA and renal failure. The EKG shows P, QRS and T-waves.
Treatment: treating the underlying condition.

Paroxysmal supraventricular tachycardia (PSVT) is a sudden increase in heart rate (usually 140-200) caused by an impulse re-entering the AV node. Some fibers of the AV node conduct at different rates. A signal is conducted to the ventricles by some fibers, then a re-entrant signal travels backward through previously unexcited nodal fibers and initiates a new impulse, resulting in a sustained tachycardia. PSVT often occurs in healthy individuals. However, the small stroke volume and cardiac output may cause light-headedness. The P-wave is buried in the QRS complex.
Treatment: in the stable patient, carotid massage is performed while an IV is started—the carotid artery is compressed and massaged with the fingers, stimulating baroreceptors and slowing the heart rate via the vagus nerve. If this is unsuccessful adenosine (Adenocard) is administered as a 6 mg rapid IV bolus, followed by a 20 cc saline flush. If there is no response in 2 minutes, 12 mg is administered.
If unsuccessful, diltiazem (Cardizem) 0.25 mg/kg (i.e. 20 mg) is given over 2 minutes, followed 15 minutes later by a second dose if conversion fails (0.35 mg/kg, or 25 mg). In the unstable patient (chest pain, hypotension), after sedation with midazolam 2 mg and morphine sulfate 2 mg, cardioversion at 50J.

Atrial fibrillation with rapid ventricular response resembles paroxysmal supraventricular tachycardia (atrial fibrillation is discussed in the section on arrhythmias).
Treatment: to control the rate in rapid atrial fibrillation, diltiazem is administered at 20 mg over 2 minutes, followed in 15 minutes by 25 mg in 2 minutes if the first dose is ineffective. In the unstable patient, cardioversion is performed at 100 joules after appropriate sedation.

Atrial flutter is a tachycardia of about 150 originating from an ectopic atrial focus depolarizing at 250 to 350 beats per minute. It is usually caused by a reentry mechanism similar to that which causes PSVT. In contrast to PSVT, it is often associated with heart disease. Symptoms may include chest pain, palpitations and light-headedness. The EKG shows “sawtooth” flutter waves preceding each QRS-complex (often 2 flutter waves precede each QRScomplex— 2:1 AV block).
Treatment: after appropriate sedation (see PSVT), cardioversion at 50 J.

Ventricular tachycardia (V-tach) is a life-threatening rapid rate (150-200) originating from an ectopic focus or foci in the ventricles. Common causes are ischemic heart disease and myocardial infarction. Symptoms may include dyspnea and chest pain. The EKG shows wide QRS-complexes.
Treatment: since V-tach implies impaired cardiac functioning, amiodarone (Cordarone) 150 mg IV is given over 10 minutes, then every 10 minutes as needed. Alternatively, lidocaine 0.75 mg/kg may be given IV push every 10 minutes, followed by a 3 mg/minute drip if converted to a normal sinus rhythm.

Common Slow Rates (Bradycardias)

A common slow rate is sinus bradycardia, with a regular rhythm below 60 beats, originating in the SA node. It is seen in physically fit individuals, but also in those on digoxin, beta-blockers, calcium-channel blockers, and in patients with cardiac disease, including myocardial infarction.
Treatment: for symptomatic patients (obdundation, hypotension), atropine is administered at 1 mg IV every 5 minutes to a maximum of .04 mg/kg. If atropine is unsuccessful, external (transcutaneous) pacing is performed until a transvenous pacemaker can be placed.
In cases of 2nd and 3rd degree AV blocks, where some or all of the fibers of the conducting system are blocked because of disease, initial therapy consists of placing an external pacemaker, followed by a transvenous and then permanent pacemaker.

Common Arrhythmias

A sinus arrhythmia originates in the SA node. The heart rate increases during inspiration and slows during expiration. It occurs normally in children and adolescents and disappears later in life.
Treatment: none.
Atrial fibrillation is a common malady in the elderly, associated with coronary artery disease, hypertension, hyperthyroidism and rheumatic heart disease. The irregular rate ranges from about 70-100. Multiple areas of the atria depolarize and contract, resulting in muscle quivering. Instead of a normal atrial depolarization (the P-wave), the EKG shows fibrillatory waves accompanied by irregular QRS-complexes.
Treatment: if the condition is recent (<48 hours), amiodarone (Cordarone) 150 mg IV over 10 min, or ibutilide (Corvert) 0.1 mg/kg IV over 10 min), is effective. If the condition is old and the rate normal, because of the high risk for embolization anticoagulation is begun with coumadin (target INR of 2.5) or aspirin for 3 weeks, depending on risk factors and age. This is followed by electrical or pharmacologic cardioversion.

Premature supraventricular contractions are extra beats originating from either the atria (premature atrial contractions—PAC’s) or the AV node (junctional premature beats). They occur in patients with and without heart disease. The EKG shows a premature P-wave in the first, and no P-wave in the latter.
Treatment: usually none is required.

Premature ventricular contractions (PVC’s) are extra beats originating from a single focus (unifocal) or different foci (multifocal) in the ventricle. Many older citizens have occasional PVC’s. The condition is aggravated by caffeine, smoking, stress and heart disease. Some cardiac drugs may cause PVC’s. The EKG shows a wide QRS without a P-wave, and the complexes are different in configuration from the normal QRS.
Treatment: efforts should be undertaken to alleviate the underlying cause(s).

Multifocal atrial tachycardia (MAT), or “wandering pacemaker”, is seen in elderly patients with chronic obstructive lung disease. In addition to the SA node, two or more different areas of the atrium act as pacemakers (ectopic foci). The EKG shows P-waves of varying morphology and changing PR intervals.
Treatment: oxygen and bronchodilators. In those with fast rates, magnesium sulfate 2 g IV over 1 minute is sometimes effective.

 


 
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