Tachyarrhythmias: Definition, Classification, Symptoms, Causes, Diagnosis and Treatments

Also called tachycardia, it is a heart rate that exceeds the normal resting rate.

Tachyarrhythmias, defined as abnormal heart rhythms with a ventricular rate of 100 or more beats per minute, are often symptomatic and generally cause patients to seek care at their provider’s office or the emergency department.

Signs and symptoms of tachyarrhythmias

Signs and symptoms related to tachyarrhythmias may include the following:

  • Shock.
  • Hypotension .
  • Heart failure .
  • Short of breath.
  • Chest pain
  • Acute myocardial infarction.
  • Palpitations and / or decreased level of consciousness.

Classification of tachyarrhythmias

The cardiac impulse is generated from the sinus node; It crosses the atrioventricular (AV) node, the bundle of His, and the Purkinje fibers and reaches the ventricles.

Tachyarrhythmias occur due to abnormal impulse generation from the sinoatrial (SA) node, AV node, or ventricles.

Furthermore, abnormal impulse generation may be associated with abnormal conduction.

Therefore, tachyarrhythmias could be classified according to rhythm (regular or irregular), site of origin (supraventricular or ventricular), and complexes on the electrocardiogram (ECG) (narrow or broad complex).

Classification of narrow or wide complex tachyarrhythmias is based on the duration of the QRS complex.

What Causes Tachyarrhythmias?

Causes of tachycardia include:

  • Heart-related conditions such as: high blood pressure (hypertension) Insufficient blood supply to the heart muscle due to coronary heart disease ( atherosclerosis ).
  • Heart valve disease.
  • Heart failure.
  • Heart muscle disease (cardiomyopathy).
  • Tumors
  • Infections

Diagnosis of tachyarrhythmias

The most common causes of sinus tachycardia, such as light planes of anesthesia, lack of adequate analgesia, dehydration, or wasting of muscle relaxation should be ruled out before considering other differential diagnoses.

Treatment should include simultaneous evaluation of the underlying causes of the particular arrhythmia.

Conventionally, cardiologists always require a 12-lead ECG to confirm the exact nature of arrhythmias. However, in the operating room, it is not always possible to obtain such an ECG.

Anesthesiologists would have to make the diagnosis by looking at the ECG monitor. Some manufacturers allow the grid lines and the simultaneous ECG of other leads to be displayed on the monitor.

The presence of a P wave will differentiate supraventricular tachycardia (SVT) from junctional tachycardia. In the presence of tachycardia, the P wave can sometimes overlap the T wave. On many occasions, changing the ECG scan speed (from 50 to 25 mm / s) can help identify the P wave.

However, even so, on several occasions, the P wave could be found to merge with the previous T wave and thus not identifiable even after altering the sweep speeds. If the origin of the impulse is above the AV node and below the SA node, the morphology of the P wave could be biphasic.

However, the absence of a P wave will not reliably rule out SVT. For example, rarely, one can find SVT along with abnormal pathways. Alternatively, several of the vagal maneuvers could be tried.

Treatment of tachyarrhythmias

Patients with hemodynamic instability or those with signs of poor tissue perfusion would be treated immediately with electrical therapy. In otherwise stable patients, the clinical benefits of immediate cardioversion in the ED are less clear.

The case for emergency cardioversion in these patients depends on the assumption that a regular sinus rhythm is preferable to the chaotic activity instituted by a tachyarrhythmia such as AF. However, the basis for such observations is primarily anecdotal patient experiences and non-randomized trial.

Patients with structural heart disease or refractory ventricular arrhythmias, despite standard antiarrhythmic therapy, may require catheter ablation.

Alternatively, the implantable cardioverter defibrillator could be used preoperatively to manage these conditions.

Epidural thoracic anesthesia can reduce the incidence of ventricular arrhythmias by blocking cardiac sympathetic fibers. Stellate ganglionectomy is another option to treat sympathetically mediated VT.

In patients undergoing thoracic surgery, thoracic epidural infusion is believed to reduce episodes of tachycardia.

When temporary pacing is necessary, the cardiologist can be called in for intervention.

Vagal manufacturers

The first line of treatment for SVTs is to try vagal maneuvers like Valsalva and carotid sinus massage (CSM). These maneuvers will be helpful only if the arrhythmia is dependent on the AV node. The Valsalva maneuver is performed by increasing intrathoracic pressure to 30–40 mmHg.

La Valsalva is generally divided into four separate phases:

  • Phase 1 : onset of effort and onset of an increase in intrathoracic pressure with glottic closure
  • Phase 2 : persistent effort and maintenance of increased intrathoracic pressure.
  • Phase 3 : release of breath and glottic pressure with a sudden drop in intrathoracic pressure.
  • Phase 4 : sudden increase in cardiac output and aortic pressure.

The rate of cardioversion with this is lower, as is the requirement for other drug management. Therefore, a postural modification of the Valsalva maneuver has been evaluated.

This included the conventional semi-reclined position during the initiation of the Valsalva maneuver, followed by the supine position and the leg lift immediately after its launch.

Carotid sinus massage

This is one of the vagal maneuvers used in the treatment of SVT.

A recent review concluded that CSM should be considered first in the treatment of SVT. CSM is performed by applying constant pressure to the right or left carotid sinus for 5–10 seconds.

Complications of CSM include stroke. Therefore, one has to rule out the presence of carotid murmur clinically before applying CSM.

Alternatively, this could be ruled out by an ultrasound examination. Recently, a prospective crossover trial concluded that ultrasound-guided CSM is a suitable alternative to classical CSM.

Periooperative management of atrial fibrillation

AF is one of the most common arrhythmias in non-cardiac surgeries, especially in the elderly. AF occurs when there is abnormal formation or propagation of impulses from the atrium due to structural or electrophysiological abnormalities.

This could be classified as acute or chronic from a management decision-making perspective. Many modalities have been tried to prevent the incidence of AF, including prophylactic beta-blockers, amiodarone, corticosteroids, and magnesium.

Acute-onset AF is usually treated. An ECG with a typical variable RR interval and absence of P waves is diagnostic of AF.

Classification of atrial fibrillation

AF is classified according to onset and duration. Paroxysmal AF is defined as AF that ends spontaneously or with any intervention within 7 days of onset.

If it persists for more than 7 days, it is defined as persistent AF. Long-term persistent AF continues for more than 12 months.

Treatment of atrial fibrillation

The treatment of AF focuses on five domains.

These include:

  • The presence of hemodynamic instability.
  • The presence of precipitating factors
  • Anticoagulation
  • Frequency control
  • Rate control.

All of these domains may not be applicable as such for first-time perioperative AF.

The first appearance of AF should be treated with the goal of restoring hemodynamic stability, while focusing on optimizing precipitating factors, rate control, and rhythm control. Anticoagulation is not the initial intraoperative focus.

Rate versus pace control

Control of drug rate is achieved with beta blockers, digoxin, verapamil, diltiazem, or a combination of drugs. Few antiarrhythmic agents such as amiodarone, dronedarone, and sotalol have both rate-control and rhythm-control properties.

Although the target for speed control is not very clear, it would generally be recommended to achieve a speed of <110 beats / min. Commonly used medications include metoprolol and esmolol, followed by diltiazem and verapamil.

These drugs are preferable to digoxin because of its rapid onset of action and also its efficacy on high sympathetic tone. Also, anesthesiologists are more familiar with these drugs than digoxin when it comes to intravenous use.

Rate control

Maintaining sinus rhythm in AF is essential to prevent long-term complications of thrombus formation and stroke. It is believed that maintaining sinus rhythm could improve the outcome.

Many trials have compared rate control alone versus rate and rhythm control and found no significant difference between the two approaches. Therefore, rhythm control may be attempted if rate control does not improve clinical symptoms.

Amiodarone is the agent commonly used to restore sinus rhythm. Before rhythm control is achieved, anticoagulation of the patient should be considered.