Bifascicular block often is asymptomatic. Possible symptoms include syncopal episodes, dizziness, thoracic pain and shortened breath. Abnormalities in the heartbeats may also be experienced, alongside a slightly decreased heart rate. The symptomatology is attributed to the hearts inability to produce a contraction forceful enough to distribute the adequate volume of blood throughout the body. Additional symptoms may be present, depending on the cause of BFB, such as symptoms related to heart failure, hypertension of a myocardial infarction.

• Asymptomatic

  Recently, an 87-year-old female with asymptomatic bifascicular block developed ventricular asystole and CHB during upper gastrointestinal (GI) endoscopy under propofol sedation at our institution. [link.springer.com]

  METHODS: Thirty-nine consecutive patients with asymptomatic chronic bifascicular block or LBBB and prolongation of the P-R interval scheduled to undergo surgery under anesthesia were prospectively enrolled in the study. [ncbi.nlm.nih.gov]

  Asymptomatic BBB was defined as the absence of any signs of dizziness or syncopes. [anesthesiology.pubs.asahq.org]

• Congestive Heart Failure

  Statistical analysis revealed that the only independent factor that could predict sudden cardiac death was the underlying congestive heart failure. [symptoma.com]

  Comparison of patients with PCD and OHD revealed a significantly lower incidence of the following clinical variables in the PCD patients (p less than 0.001): exertional angina, dyspnea, congestive heart failure, cardiomegaly, functional class I (all by [ncbi.nlm.nih.gov]

  Some medications are associated with heart blocks, and this disorder is most common among people with other heart problems, like congestive heart failure or myocardial infraction. [wisegeek.org]

• Weakness

  […] abdominal pain fever fast heart rate heart stops beating ( sinus pause/arrest) vomiting diarrhea stomach pain lack of appetite rash double vision reduced sense of touch numbness and tingling muscular weakness loss of full control of bodily movements [rxlist.com]

  Case Report A 26-year-old female presented with complains of weakness and low-grade fever for last 1½ months. She also complained of gum bleeding ad menorrhagia for last 15 days. [amhsjournal.org]

  […] based on these data: pacemaker therapy is indicated if the HV interval exceeds 70 ms in syncope, or if an electrophysiologic study performed for other reasons happens to find an HV interval ≥100 ms. 4 Unfortunately, these old studies 2,3 had several weaknesses [revespcardiol.org]

  Other symptoms that are noted occasionally include personality changes, irritability, fleeting memory losses, generalized weakness or fatigue, muscle aches, slurred speech, and insomnia. Physical examination. [tele.med.ru]

  Other patients can be relatively asymptomatic and have minimal symptoms other than dizziness, weakness, or malaise. Third-degree AV block may be an underlying condition in patients who present with sudden cardiac death. [emedicine.medscape.com]

• Collapse

  In older patients this finding may be accompanied with collapses. A relatively rare complication of a bifascicular block is the emergence of third-degree AV block. [health-tutor.com]

  On examination, pulse was 104/min regular, high volume, collapsing,Blood pressurewas130/64 mm HgandRRrespiratory rate was20/min regular and he was afebrile. [thetrp.net]

  Prognosis Patients with third-degree atrioventricular (AV) block (complete heart block) are frequently hemodynamically unstable; as a result, they may experience syncope, hypotension, cardiovascular collapse, or death. [emedicine.medscape.com]

• Unconsciousness

  If the bifascicular block is accompanied with periods of unconsciousness, it is advisable to perform permanent pacing. [health-tutor.com]

  2011 Key Record Dates Last Update Posted: January 6, 2016 Last Verified: October 2011 Keywords provided by Boston Scientific Corporation: Syncope Bifascicular block Bradycardia pacing Additional relevant MeSH terms: Layout table for MeSH terms Syncope Unconsciousness [clinicaltrials.gov]

  […] blood cell count low blood platelet count hives redness and peeling of the skin itching hair loss eye pain/irritation sun sensitivity rapid, involuntary eye movement twitching weakness change in taste dry mouth convulsions impotence speech disorder near-unconsciousness [rxlist.com]

• Nausea

  She had nausea and was hypotensive. The attack was terminated by administration of amiodarone 300 mg intravenously. On x-ray examination, the heart silhouette was diffusely enlarged. [the-medical-dictionary.com]

  En route to the scene, dispatch advises you that a 66 year old male is complaining of a fall with injury, chest pain, left arm pain, and nausea. On arrival, the patient is standing in his kitchen. He is pale and extremely diaphoretic. [ems12lead.com]

  HPI: 90 yo male with PMH of HTN, DM presents to ED with 2-3 weeks of lower extremity edema and intermittent chest pain, with acute worsening of cardiac chest pain yesterday and this morning, now accompanied by SOB, nausea, and lightheadedness. [cmcedmasters.com]

  Side effects of flecainide include: visual disturbances dizziness irregular heartbeat (arrhythmias) swelling weakness strong or irregular heartbeat ( palpitations ) fatigue shakiness ( tremors ) constipation nausea chest pain shortness of breath headache [rxlist.com]

  Classically, it is preceded by a prodrome of nausea and diaphoresis and is associated with severe bradycardia. Episodes usually are triggered by pain, anxiety, or stress. A family history of syncope may be present. [aafp.org]

• Heart Block

  The highest incidence of complete heart block occurred in right bundle-branch block and left axis deviation when associated with heart disease, but the annual rate was only 4%/yr. [ncbi.nlm.nih.gov]

  Perioperative risk of complete heart block in patients with bifascicular block and prolonged PR interval. [thorax.bmj.com]

  See heart block. 2. a type of heart block in which the blocking is at the atrioventricular junction. [medical-dictionary.thefreedictionary.com]

• Heart Disease

  Initially, 62% of the total group had evidence of heart disease. [ncbi.nlm.nih.gov]

  Stay on top of the latest advances in molecular imaging, intravascular ultrasound, cardiovascular regeneration and tissue engineering, device therapy for advanced heart failure, atrial fibrillation management, structural heart disease, Chagasic heart [books.google.com]

  Aortic stenosis Anterior MI (occurs in 5-7% of acute AMI) Primary degenerative disease of the conducting system (Lenegre’s / Lev’s disease) Congenital heart disease Hyperkalaemia (resolves with treatment) Related Topics Left anterior fascicular block [litfl.com]

  Bundle Branch Block Left bundle branch block and right bundle branch block of recent onset, indicate the need for a cardiovascular examination to rule out heart disease, especially ischemic heart disease. [ucalgary.ca]

  Their mean age was 73 years, 47% presented with a structural heart disease, 66% had hypertension, 30% had diabetes, and another 30% had dyslipaemia. [academic.oup.com]

• Tachycardia

  EPS demonstrated inducible ventricular tachycardia (VT) in four patients, an HV interval greater than or equal to 70 msec in four, intra- and infra-His block with atrial pacing in one, and was nondiagnostic in four patients. [ncbi.nlm.nih.gov]

  Ventricular Pre-excitation syndrome Lown–Ganong–Levine Wolff–Parkinson–White Flutter / fibrillation Atrial flutter Ventricular flutter Atrial fibrillation Familial Ventricular fibrillation Pacemaker Ectopic pacemaker / Ectopic beat Multifocal atrial tachycardia [en.wikipedia.org]

  (PSVT) (Medical Encyclopedia) Ventricular tachycardia (Medical Encyclopedia) Wolff-Parkinson-White syndrome (Medical Encyclopedia) [ Read More ] [icdlist.com]

  Wide complex tachycardia with RBBB morphology in lead V1 and left axis deviation. [ecgmedicaltraining.com]

  […] between ventricular tachycardia and preexcited tachycardia, Clin Cardiol, 1994, vol. 17 (pg. 306 - 8 ) 49 Electrophysiology: ventricular tachycardia: diagnosis of broad QRS complex tachycardia, Heart, 2001, vol. 86 (pg. 579 - 85 ) Published on behalf [academic.oup.com]

• Heart Failure

  […] syndrome Other Cardiac fibrosis Heart failure Diastolic heart failure Cardiac asthma Rheumatic fever This article about a medical condition affecting the circulatory system is a stub. [en.wikipedia.org]

  […] for the Evaluation and Management of Heart Failure... ‏ [books.google.com]

  The following were more frequent in the SCD group (P < .05): angina, previous myocardial infarction, heart failure, cardiomegaly, left bundle-branch block, premature ventricular beats, and ventricular tachycardia. [scholars.northwestern.edu]

  Seven patients died (follow-up 27.3 +/- 32 months), five from heart failure. [ncbi.nlm.nih.gov]

• Hypertension

  Additional symptoms may be present, depending on the cause of BFB, such as symptoms related to heart failure, hypertension of a myocardial infarction. [symptoma.com]

  In addition, right atrial hypertension of longstanding may produce cyanosis because of right-left shunting through a patent foramen ovale. [ncbi.nlm.nih.gov]

  Coronary artery disease, hypertension or heart attacks are some of the contributing factors. Treatment for bifascicular block includes managing these conditions. [wisegeekhealth.com]

  In men younger than 60 years, RBBB had significant relationships with hypertension, elevated fasting glucose and increased heart size. There was a relationship between hypertension and RBBB in women younger than 60 years. [kjim.org]

• Euphoria

  […] involuntary eye movement twitching weakness change in taste dry mouth convulsions impotence speech disorder near-unconsciousness (stupor) nerve pain pneumonitis/ pulmonary infiltration amnesia confusion decreased sex drive ( libido ) depersonalization euphoria [rxlist.com]

• Slurred Speech

  Other symptoms that are noted occasionally include personality changes, irritability, fleeting memory losses, generalized weakness or fatigue, muscle aches, slurred speech, and insomnia. Physical examination. [tele.med.ru]

A bifascicular block is diagnosed via an electrocardiogram, carried out due to BFB suspicion or for other suspected diseases. An echocardiogram will help to illustrate cardiac functionality, once the ECG findings reveal signs compatible with a BFB.
An electrophysiological study can also corroborate the findings of the aforementioned procedures. His bundle electrograms [H] are used in order to track the duration of conduction intervals and atrial incremental pacing is also applied. The latter usually leads to the detection of AV nodal Wenckebach periodicity, which could lead to an atrioventricular block and sudden cardiac death.

• Wide QRS Complex

  An AV block at the level of the bundle branches will result in an idioventricular escape rhythm – wide QRS complexes with very slow rates – which is a low-output rhythm. [ecgguru.com]

  Mont L. et al: A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 83:1649, 1991. ‎ [books.google.de]

  The QRS complexes are wide both due to preexcitation and due to right bundle branch block, which persists during preexcitation. [the-medical-dictionary.com]

  Wenckebach block is usually due to block within the AV node, with a narrow QRS complex. On the other hand, Mobitz II is generally associated with a wide QRS complex, due to infranodal disease. [thecardiologyadvisor.com]

• Bifascicular Block

  The ICD code I452 is used to code Bifascicular block Bifascicular block is a conduction abnormality in the heart where two of the three main fascicles of the His/Purkinje system are blocked. [icd.codes]

  Since marked H-Q prolongation in conducted sinus beats was documented in nearly all patients with bifascicular block associated with intermittent complete trifascicular block, we conclude that a considerably lengthened H-Q interval in bifascicular block [ncbi.nlm.nih.gov]

  What are the symptoms of bifascicular block?It is very common for a bifascicular block to produce no symptoms at all. [symptoma.com]

• Right Bundle Branch Block

  Equivalent ICD-9 Codes GENERAL EQUIVALENCE MAPPINGS (GEM) Right bundle branch block and left posterior fascicular block (approximate match) Right bundle branch block and left anterior fascicular block (approximate match) Other bilateral bundle branch [icd.codes]

  block Right bundle branch block AND incomplete left bundle branch block Right bundle branch block with left bundle branch block Right bundle branch block, anterior fascicular block AND incomplete posterior fascicular block Clinical Information An electrocardiographic [icd9data.com]

  Types of Bifascicular Blocks Right bundle branch block + left anterior fascicular block. Right bundle branch block + left posterior ascicular block. Complete left bundle branch block : Equivalent to the block of both fascicles. [en.my-ekg.com]

  The highest frequency of heart disease was in patients with left bundle-branch block and first-degree atrioventricular block (78% or 22/28), while the lowest was in those with right bundle-branch block and left axis deviation (56% or 55/98). [ncbi.nlm.nih.gov]

  branch block Bilateral bundle branch block (heart rhythm condition) Heart block Right bundle branch block and left anterior fascicular Right bundle branch block and left anterior fascicular block Right bundle branch block and left posterior fascicular [icd10data.com]

• Complete Left Bundle Branch Block

  Types of Bifascicular Blocks Right bundle branch block + left anterior fascicular block. Right bundle branch block + left posterior ascicular block. Complete left bundle branch block : Equivalent to the block of both fascicles. [en.my-ekg.com]

  If you were diagnosed at age 39 or younger, these include: Complete right bundle branch block (CRBBB) Complete left bundle branch block (CLBBB) Complete right bundle branch block with left hemiblock, also known as a Bifascicular block Should you have [lifeinsurancepost.com]

  Am J Cardiol, 1996, vol. 77 (pg. 1185 - 90 ) 4 The prognosis of complete left bundle branch block, Am Heart J, 1965, vol. 70 (pg. 157 - 9 ) 5 A prospective study of sudden death in ‘high-risk’ bundle-branch block, N Engl J Med, 1978, vol. 299 (pg. 209 [academic.oup.com]

  Chronic Bifascicular Or Trifascicular Block Patients with chronic bifascicular block (right bundle branch block and left anterior hemiblock, right bundle branch block and left posterior hemiblock, or complete left bundle branch block) and patients with [arthritisresearch.us]

  In this study, the different types of bifascicular block had differing rates of progression to complete AV block: the incidence was 44/124 (35%) in left anterior hemiblock plus right bundle branch block (LAHB+RBBB), 47/102 (46%) in complete left bundle [revespcardiol.org]

• AV Block Mobitz II

  […] of consciousness (c) Non-commercial drivers with (i) second degree AV block; Mobitz II (distal AV block) (ii) alternating LBBB and RBBB, or (iii) acquired third degree AV block are not eligible for a licence Conditions for maintaining licence None Reassessment [ucalgary.ca]

  Conduction Terminology Type I second-degree AV block = Mobitz I block = Wenckebach block Type II second-degree AV block = Mobitz II block Third-degree AV block = complete heart block Left anterior fascicular block = left anterior hemiblock Left posterior [thecardiologyadvisor.com]

  Permanent pacemaker implantation is indicated for the following [21] : Advanced second-degree AV block or intermittent third-degree AV block Mobitz II second-degree AV block Alternating bundle-branch block Class IIa recommendations Permanent pacemaker [emedicine.medscape.com]

  Borderline asymptomatic arrhythmias were defined as follows: less than 10 seconds of second- or third-degree AV block (Mobitz II); or heart rate less than 30 beats/min for less than 10 seconds while asleep. [em-consulte.com]

• AV Block Mobitz I

  […] bundle branch block (LBBB) (ii) bifascicular block (iii) second degree AV block/Mobitz I (iv) first degree AV block + bifascicular block, or (v) congenital third degree AV block are eligible for a licence if they have had no associated impaired level [ucalgary.ca]

  Conduction Terminology Type I second-degree AV block = Mobitz I block = Wenckebach block Type II second-degree AV block = Mobitz II block Third-degree AV block = complete heart block Left anterior fascicular block = left anterior hemiblock Left posterior [thecardiologyadvisor.com]

Most patients do not require any type of treatment for BFB and frequent monitoring suffices to track the progression of the condition. Lifestyle adaptations can help an individual cope better and include dietary changes, physical exercise, smoking cessation and weight loss. The underlying conditions that have led to the occurrence of BFB should, however, be treated with a variety of medications targeting each disease. Drugs used against hypercholesterolemia, anti-hypertensive medications, drugs to prevent blood clotting and angioplasty are all potential treatments used to manage the underlying disease. Patients who have a medical history of syncopal episodes may need a pacemaker in order to restore the normal heart rate.

A 2006 study [12] evaluated 100 individuals with an average age of 68 years old and affected by bifascicular block: 50% had previously experienced a syncopal episode and patients categorized under the NYHA 4 category were not included in the study. The follow-up procedure lasted for 7 years and comprised electrocardiographic tests, Holter monitoring and electrophysiological assessment. Statistical analysis revealed that the only independent factor that could predict sudden cardiac death was the underlying congestive heart failure. The severity of congestive heart failure is therefore deemed as an unfavorable prognostic marker amongst people who are diagnosed with BFB.

There is a variety of possible causes leading to a bifascicular block. The primary causes include:

• Congenital cardiac abnormalities
• Medications
• Heart traumatization due to an infarction or surgical procedure
• Vascular disorders, such as hypertension or coagulopathy causing excessive clotting

Bifascicular block tends to more frequently affect people as their age increases; its prevalence has been estimated at approximately 0,1% amongst individuals aged < 35 years old and 1% amongst patients older than 35 years old [6] [7]. It has been detected in around 8% of the patients hospitalized for a syncopal episode [8] and is frequently accompanied by various coexistent disorders such as coronary heart disease and hypertension. Mortality rates are high amongst these patient sub-categories and are estimated to amount to up to 12% [9] [10]. A study [11] that monitored 260 patients with BFB calculated that the most prevalent comorbidity amongst them was hypertension, followed by structural heart disease, diabetes and dyslipidemia. Average survival was estimated to be approximately 5 years and 20% of them eventually succumbed (7% due to heart dysfunction). It is believed that heart failure corresponding to the NYHA ≥2 category and accompanied by renal insufficiency constitute bad prognostic markers for people with a BFB.

In order to comprehend the pathophysiological mechanisms of a bifascicular block, it is important to briefly outline the route of the electric cardiac signal. An impulse is normally generated in a specific location of the right atrium, the sinoatrial node (SA) and proceeds further below to the atrioventricular node (AV), which is found in-between the left and right atria. A slight delay of transmission occurs in the AV node and the impulse is then transferred to the bundle of His, which consists of a single right bundle branch and two left bundle branches (anterior and posterior). Finally, the Purkinje fibers receive the electrical transmission and are responsible for a coordinated contraction which involves the entire ventricles.

A bifascicular block essentially involves a failure of the signal to be transmitted through the right fascicle and one of the two left fascicles; alternatively, the impulse may fail to travel down through both of the left fascicles. Either way, when signal transmission is blocked in two of the three fascicles, the phenomenon is termed a bifascicular block. If a BFB occurs after a myocardial infarction, it is an indicator of severe myocardial damage.

Blockages can generally occur in a single fascicle as well. A failure for the signal to be transmitted through the anterior or posterior fascicle of the left bundle branch leads to a left anterior or posterior hemiblock respectively.

Bifascicular block cannot be prevented. Appropriate management, however, of the underlying cause may help to minimize its occurrence.

The electrical impulse of each heartbeat is generated in the sinoatrial node of the right atrium. It is then transmitted to the atrioventricular node and, finally, through the bundle of His (left and right), it reaches the Purkinje fibers throughout the myocardium, which are responsible for a contraction. The bundle of His is divided into the right bundle branch (one fascicle) and the left bundle branch (anterior and posterior bundle branch). A bifascicular block (BFB) involves a signal blockage in the right bundle branch and in either the anterior or posterior left bundle branch, according to the American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) [1]. European guidelines frequently use the term left bundle branch block (LBBB) in order to define a bifascicular block, since it is believed to encompass a blockage in both its fascicles [1] [2]. Another sub-type involves a bifascicular block with a prolonged PR interval, many times mistakenly referred to as a "trifascicular block". Although American guidelines generally advise against the use of the terms bifascicular and trifascicular block [3], they are still frequently used today by many physicians. In general, a bifascicular block is any conduction failure affecting any two of the three bundle branches of the His bundle.

In rare occasions, a bifascicular block or its counterpart which involves a prolonged PR interval as well, can progress to a complete cardiac block; the possibility of this happening is rather scarce, as outlines by a study that documented 1 patient out of the 550 monitored eventually developed a complete heart block [4] [5].

BFB frequently remains unsymptomatic and is detected incidentally. In some patients it might produce symptoms, such as dizziness, fainting, chest pain and arrhythmias. Heart rate is usually decreased.

Bifascicular block may remain untreated and monitoring is adequate for the patient follow-up. Lifestyle changes and medication used to control the underlying cause can be applied as supportive measures. Pacemakers are used only in cases of individuals who experience frequent fainting.

What is a bifascicular block (BFB)?
The heart functions like an electrical pump. Each beat starts as an electrical impulse in one of the top chambers of the heart, travels to the area located in the middle of the organ and is then transmitted to the ventricles, the cavities that contract, through 3 passages called fascicles. These are the right bundle branch and the two left bundle branches; all together, they form the His bundle. The His bundle is a vital electrical path which carries the impulse from the location where it is generated to the rest of the heart so that a beat can be produced and the blood can be pumped throughout the body. A bifascicular block involves a blockage of the signal in two of the three branches of the His bundle.

What causes bifascicular block?
People can be born with a bifascicular block, due to congenital abnormalities of the conduction passages in the heart. Most often, however, BFB occurs as a complication of another disease, such as hypertension, heart attack, congestive heart failure, heart surgery or as a side effect of some medications.

What are the symptoms of bifascicular block?
It is very common for a bifascicular block to produce no symptoms at all. However, since two of the three fascicles do not conduct the signal to some parts of the heart, so that they can contract, the heartbeats can be irregular. Dizziness, fainting, chest pain and shortness of breath may also be experienced. The heart rate can be slower than normal and a severe complication of BFB is sudden cardiac death: instant death that is a result of a heart condition. People with severe congestive heart failure are in greater risk of dying from sudden cardiac death.

How is bifascicular block diagnosed and treated?
Bifascicular block can be diagnosed via an electrocardiogram and an echocardiogram. Both are non-invasive procedures and can accurately diagnose the condition. In most of the cases it does not need to be treated. Patients may receive treatment for the BGB itself if it causes fainting. Medications and other procedures are used to treat the underlying causes that led to BFB.

1. Epstein AE, DiMarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices): developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation 2008; 117:e350.
2. Task Force for the Diagnosis and Management of Syncope, European Society of Cardiology (ESC), European Heart Rhythm Association (EHRA), et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J 2009; 30:2631.
3. Surawicz B, Childers R, Deal BJ, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology. Circulation 2009; 119:e235.
4. McAnulty JH, Rahimtoola SH, Murphy E, et al. Natural history of "high-risk" bundle-branch block: final report of a prospective study. N Engl J Med 1982; 307:137.
5. Schneider JF, Thomas HE, Kreger BE, et al. Newly acquired right bundle-branch block: The Framingham Study. Ann Intern Med 1980; 92:37.
6. Schneider JF, Thomas HE, Kreger BE, McNamara PM, Kannel WE. Newly acquired left bundle branch block: the Framingham study. Ann Intern Med 1979; 90(3):303-310.
7. Rotman M, Triebunasser JH. A clinical and follow up study of right and left bundle branch block.Circulation, 1995; 51:477-484.
8. Englund A, Bergfeldt L, Rehnqvist N, Astrom H, Rosenqvist M. Diagnostic Value of programmed ventricular stimulation in patients with bifascicular block: a prospective study of patients with and without syncope. J Am Coll Cardiol, 1995; 26(6):1508-1515.
9. Dhingra RC, Palileo E, Strasberg B, et al.Significance of the HV interval in 517 patients with chronic bifascicular block.Circulation, 1981; 64(6):1265-1271.
10. McAnulty JH, Rahimtoola SH. Bundle branch block Prog Cardiovasc.Dis 1984; 26(4):333-354.
11. Marti-Almor J, Cladellas M, Bazan V, et al. Long-term mortality predictors in patients with chronic bifascicular block. Europace 2009;11:1201-7.
12. Tabrizi F, Rosenqvist M, Bergfeldt L, Englund A. Long-term prognosis in patients with bifascicular block--the predictive value of noninvasive and invasive assessment. J Intern Med. 2006 Jul;260(1):31-8.