Eletrocardiograma II Calcule a frequência cardíaca do ECG abaixo.

Patologias ligada ao ritmo cardíaco Avaliação pelo ECG

Parada/Pausa Sinusal - Falha na descarga do nó sinusal Sinus Arrest occurs when there is a pause in the rate at which the SA node fires. With sinus arrest, there is no relationship between the pause and the basic cycle length. - Falha na descarga do nó sinusal - Períodos de ausência de despolarização atrial - Períodos de assistolia

Síndrome Bradi / Taqui - Episódios Intermitentes de frequências lentas e rápidas provenientes do nó sinusal ou de outros focos atriais - Bradi <60 BPM - Taqui >100 BPM Brady/Tachy syndrome occurs when the SA node has alternating periods of firing too slowly (< 60 BPM) and too fast (>100 BPM). Brady/Tachy syndrome often manifests itself in periods of atrial tachycardia, flutter, or fibrillation. Cessation of the tachycardia is often followed by long pauses from the SA node.

Bloqueio AV de Primeiro Grau - Condução retardada através do nó AV - Intervalo PR > 0,20 seg. - FC normal e regular AV block can be described as a prolongation of the PR interval, the interval from the onset of the P-wave to the onset of the QRS complex. First-degree AV block is defined by a PR interval greater than 0.20 seconds (200 ms). First-degree AV block can be thought of as a delay in AV conduction, but each atrial signal is conducted to the ventricles (1:1 ratio).

Bloqueio AV de Segundo Grau – Mobitz II P - QRS P - QRS P P - QRS P - QRS - Atraso na condução infranodal, portanto as ondas P são bloqueadas subitamente, sem variabilidade prévia do PR - Onda P não conduz a cada 2 estímulos ou mais (2:1, 3:1) Mobitz Type II Second-Degree AV block refers to intermittent dropped beats preceded by constant PR intervals. To differentiate Mobitz I from Mobitz II, note the PR interval in the beats preceding and following the dropped beat. If a difference between these two PR intervals is more than 0.02 seconds (20 ms), then it is Mobitz I. If the difference is less than 0.02 seconds, then it is Mobitz II. The infranodal (His bundle) tissue is most commonly the site of Mobitz II block. *Note: Advanced second-degree block refers to the block of two or more consecutive P-waves (i.e., 3:1 block).

Bloqueio AV de Terceiro Grau - Ausência de condução dos átrios para os ventrículos, gerando ondas P e QRS totalmente dissociados Frequência Ventricular = baixa Frequência Atrial = normal/alta Intervalo PR = variável - Requer uso de Marcapasso! Third-Degree AV block is also referred to as complete heart block. It is characterized by a complete dissociation between P-waves and QRS complexes. The QRS complexes are not caused by conduction of the P-waves through the AV node to the ventricles. In Third-Degree AV block, the QRS is initiated at a site below the AV node (such as in the His bundle or the Purkinje fibers). This “escape rhythm” is normally 40–60 BPM if initiated by the His bundle (a junctional rhythm) and <40 BPM if initiated by the Purkinje fibers.

Taquicardia Sinusal Origem: Nó Sinusal; Frequência > 100 bpm In Sinus Tachycardia, the EKG deflection will show a normal P and R-wave depolarization, with a rapid tachycardic rate Sinus Tachycardia rates range between 100-180 BPM The underlying Mechanism for Sinus Tachycardia is Abnormal Automaticity (Hyper-Automaticity) Origem: Nó Sinusal; Frequência > 100 bpm Mecanismo: descarga adrenérgica (ansiedade, exercício físico), febre, ICC

Taquicardia Atrial Origem: Átrio – Focos Ectópicos Atrial Tachycardia is defined as a series of 3 more consecutive atrial premature beats occurring at a rate of >100 BPM. Atrial tachycardia is usually paroxysmal (PAT – Paroxysmal atrial tachycardia), it starts and ends abruptly. It can occur in healthy as well as diseased hearts and may result from emotional stress or excessive use of alcohol, tobacco, or caffeine. Origin: Ectopic focus located in the atrium Mechanism: Abnormal Automaticity Origem: Átrio – Focos Ectópicos Frequência:>100 bpm Mecanismo: Automaticidade Anormal

Fibrilação Atrial (FA) Origem: Átrios D e E; Mecanismo: múltiplas pequenas ondas de reentrada Características: Ondas P com morfologias diferentes, associado a um ritmo ventricular irregular; ritmo caótico - átrio tremendo; Atrial Fibrillation (AF) is characterized by random, chaotic contractions of the atrial myocardium. Patients have an atrial rate of 400 BPM or more, often too fast to measure on an EKG. A surface EKG shows atrial fibrillation as irregular, wavy deflections (fibrillatory waves) between narrow QRS complexes. The fibrillatory waves vary in shape, amplitude, and direction. The chaotic nature of atrial fibrillation results in a grossly irregular ventricular rhythm. The rhythm is considered controlled if the ventricular rate is less than 100 BPM; uncontrolled if the ventricular rate conducts to greater than 100 BPM. Mechanism: In AF, the multiple wavelets of reentry do not allow the atria to organize. The ectopic focus or foci are said to be located around or within the pulmonary veins. Drugs such as flecainide, sotalol and amiodarone can terminate and prevent atrial fibrillation. Drug therapy can be used before or after DC cardioversion to maintain sinus rhythm after cardioversion.

Fibrilação Atrial (FA) The primary mechanism of atrial fibrillation is thought to be multiple wavelet reentry. It occurs when adjacent cells in the atrial myocardium have different refractory periods (uneven recovery times). During multiple wavelet reentry: An electrical impulse passing through the atrial myocardium depolarizes excitable cells and moves around refractory cells The rerouted electrical impulse then stimulates any adjacent cells that have recovered their excitability By this time, the cells first stimulated are again excitable. The electrical impulse re-excites the cells and continues to move through the atria, exciting and re-exciting the cells it encounters Unlike a normal depolarization wave that travels from cell to cell in one direction, reentry waves wander across the myocardium, randomly splitting off and following different reentrant pathways (see illustration). This random movement causes the chaotic, uncoordinated contractions of atrial fibrillation.

Fibrilação Ventricular (FV) Origem: Ventrículo Mecanismo: Múltiplas pequenas ondas de reentrada Características: Despolarização “incoordenada” dos ventrículos, resultando na interrupção do DC = Ritmo de PCR The following EKG findings help electrophysiologists to diagnose VF: P-waves and QRS complexes are not present Heart rhythm is highly irregular The heart rate is not defined (without QRS complexes) While multiple wavelets of reentry maintain VF, there is some belief that focal activation initiates it.