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Bundle branch block
Pulseless electrical activity
Atrioventricular nodal reentrant tachycardia (AVNRT)
Premature atrial contraction
Long QT syndrome and Torsade de pointes
Premature ventricular contraction
Rheumatic heart disease
Atrial septal defect
Coarctation of the aorta
Patent ductus arteriosus
Ventricular septal defect
Hypoplastic left heart syndrome
Tetralogy of Fallot
Total anomalous pulmonary venous return
Transposition of the great vessels
Pericarditis and pericardial effusion
Aortic valve disease
Mitral valve disease
Pulmonary valve disease
Tricuspid valve disease
Coronary steal syndrome
Polycystic kidney disease
Renal artery stenosis
Peripheral artery disease
Subclavian steal syndrome
Superior mesenteric artery syndrome
Human herpesvirus 8 (Kaposi sarcoma)
Chronic venous insufficiency
Deep vein thrombosis
Acyanotic congenital heart defects: Pathology review
Aortic dissections and aneurysms: Pathology review
Atherosclerosis and arteriosclerosis: Pathology review
Cardiac and vascular tumors: Pathology review
Cardiomyopathies: Pathology review
Coronary artery disease: Pathology review
Cyanotic congenital heart defects: Pathology review
Dyslipidemias: Pathology review
Endocarditis: Pathology review
Heart blocks: Pathology review
Heart failure: Pathology review
Hypertension: Pathology review
Pericardial disease: Pathology review
Peripheral artery disease: Pathology review
Shock: Pathology review
Supraventricular arrhythmias: Pathology review
Valvular heart disease: Pathology review
Vasculitis: Pathology review
Ventricular arrhythmias: Pathology review
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Wolff-Parkinson-White syndrome p. 312
Wolff-Parkinson-White pattern, or WPW, is a type of heart arrhythmia caused by an accessory pathway, or an extra electrical conduction pathway, connecting the atria and ventricles, or the upper and lower chambers of the heart.
Normally, an electrical signal starts at the sinoatrial node, or SA node, in the right atrium. It then propagates out through both atria, including bachmann’s bundle in the left atrium, and contracts both atria. Then, it’s delayed just a little bit as it goes through the atrioventricular node, or AV node, before it passes through the Bundle of His and to the Purkinje fibers of the left and right ventricles, causing them to contract as well.
On an electrocardiogram, the P-wave corresponds to atrial contraction, the PR interval corresponds to the slight delay through the AV node, and the QRS complex corresponds to ventricular contraction.
Now, in a normal electrical conduction system, the AV node is the only place where the signal can get through to the ventricles from the atria. It’s kind of like there’s a gatekeeper that has to stop the signal and make sure everything’s good before letting it pass, so there’s always a slight delay here. People with WPW essentially have a secret, backdoor entrance. Because this entrance is secret, it doesn’t have a gatekeeper; therefore, there’s no delay as the signal moves through it. This secret backdoor entrance is a tiny bundle of cardiac tissue that conducts electrical signals really well, called the Bundle of Kent. Using the Bundle of Kent means the ventricles start to contract a little bit early, which is called pre-excitation. If the Bundle is on the left side of the heart, it’s called “type A pre-excitation.” If it’s on the right side, it’s called “type B pre-excitation.” Type A, on the left side, is a lot more common.
All right, even though one signal sneaks through early, the other signal waiting at the AV node eventually makes its way through, and the two signals essentially combine to contract the ventricles. So, on an ECG, people with WPW have a short PR interval with a delta wave, as well as QRS prolongation, which makes sense because the signal’s taking the shortcut and contracting the ventricles early. This means the PR interval is shorter, and the overall QRS complex is longer. People with WPW usually have a PR interval less than 120 ms and a QRS complex greater than 110 ms. Also, the ST segment and T wave, which represent repolarization, will often be directly opposite the QRS complex. This WPW pattern doesn’t typically cause any symptoms and is relatively benign.
However, in some cases, this pattern can facilitate certain arrhythmias, make certain arrhythmias more severe, and potentially even cause sudden cardiac death. When this happens, it’s called Wolff-Parkinson-White syndrome. For example, people with atrial arrhythmias might have atrial rates in the 200 to 300 beats per minute range. Normally, the AV node doesn’t allow all of these signals through, and so the ventricles will contract at a lower number; for example, for every three atrial beats, there’s only one ventricular beat, so for 300 beats per minute in the atrium, the ventricle would go for 100 beats per minute.
Wolff-Parkinson-White pattern (WPW) is a congenital disorder, in which there is heart arrhythmia caused by an extra electrical conduction pathway, called the Bundle of Kent, connecting the atria and ventricles. This can cause the ventricles to contract earlier, leading to pre-excitation, a short PR interval with a delta wave, and QRS prolongation on an electrocardiogram. While WPW is usually benign, it can lead to dangerous arrhythmias, such as atrioventricular reentrant tachycardia (AVRT), which can cause sudden cardiac death.
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