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	QT interval - Wikipedia, the free encyclopedia
		In medicine, specifically cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle.
		The QT interval is dependent of the heart rate and has to be corrected.
		where QTc is the QT interval corrected for rate, and RR is the interval from the onset of one QRS complex to the onset of the next QRS complex, measured in seconds.
	en.wikipedia.org /wiki/QT_interval (264 words)

	What is QT interval prolongation? Journal of Family Practice - Find Articles
		QT interval prolongation is an irregularity of the electrical activity of the heart that places patients at risk for ventricular arrhythmias.
		QT interval prolongation is an abnormality of the electrical activity of the heart that places individuals at risk for ventricular arrhythmias.
		The QT interval represents the duration of the ventricular action potential and is measured from the beginning of depolarization (Q wave) until the end of repolarization (T wave, FIGURE 1).
	www.findarticles.com /p/articles/mi_m0689/is_6_54/ai_n14732743 (842 words)

	Diabetes and the QT Interval
		QT interval is affected by CHD and autonomic neuropathy and it is possible that these new diabetic patients with prolonged QT interval and increased QTd may have had undiagnosed neuropathy or CHD.
		The prognostic value of the QT interval and QT interval dispersion in all-cause and cardiac mortality and morbidity in a population of Danish citizens.
		QT and QTc dispersion are accurate predictors of cardiac death in newly diagnosed non-insulin-dependent diabetes: cohort study.
	www.arabmedmag.com /issue-15-12-2004/cardiology/main01.htm (3278 words)

	qt interval MA from SA
		Serious consideration should be given to an Italian study entitled "Prolongation of the QT Interval and the Sudden Infant Death Syndrome," appearing in the June 11, 1998 edition of the New England Journal of Medicine.
		According to the study, inability to shorten the QT interval during increases in heart rate may be involved in SIDS.
		We do not even know if the long QT interval is causing the deaths of these babies, as it does in older people--or whether it is a marker for something that is happening in the body, for example, in the nervous system.
	sids-network.org /experts/qtintervalsama.htm (883 words)

	QT interval is a heritable quantitative trait with evidence of linkage to chromosome 3 in a genome-wide linkage ...
		QT interval is a heritable quantitative trait with evidence of linkage to chromosome 3 in a genome-wide linkage analysis: The Framingham Heart Study
		BACKGROUND: QT interval prolongation is associated with increased risk of sudden cardiac death and coronary heart disease and may result from acquired conditions or inherited ion channel defects.
		Further studies are warranted to identify genes that influence QT interval variation and to determine the role of heritable factors in life-threatening QT prolongation.
	cardiogenomics.med.harvard.edu /publication-detail?publication_id=1220 (372 words)

	Drug-induced Prolongation of the QT Interval - January 1, 2005 - American Family Physician
		The risk of torsades de pointes is not related linearly to the degree of QT prolongation, although any drug that prolongs the QT interval beyond 500 msec is thought to confer an elevated risk.
		QT prolongation occurs when a drug or congenital syndrome affects ion channels in cardiac cells and leads to prolongation of the action potential during depolarization.
		The author concludes that when physicians need to use a medication known to have the effect of prolonging the QT interval, a review of other risk factors that may increase the likelihood that torsades de pointes will develop is recommended.
	www.aafp.org /afp/20050101/tips/7.html (635 words)

	QT interval and QT dispersion increase in the elderly during laparoscopic cholecystectomy: a preliminary study: ...
		QT interval and QT dispersion increase in the elderly during laparoscopic cholecystectomy: a preliminary study: [L'intervalle QT et la dispersion du QT s'accentuent chez les patients ages pendant la cholecystectomie laparoscopique : une etude preliminaire] -- Egawa et al.
		QT interval and QT dispersion increase in the elderly during laparoscopic cholecystectomy: a preliminary study
		with increases in the QT interval and the QTD in the elderly.
	www.cja-jca.org /cgi/content/full/49/8/805 (1814 words)

	Measuring the QT Interval
		In general, the QT interval lengthens as the heart rate slows, and shortens as the heart rate increases.
		In the normal sinus range of 60 to 100, the QT Interval should be approximately 1/2 of the preceding R to R interval.
		A prolonged QT interval represents a delay in repolarization of the ventricles.
	www.med.umich.edu /ccmu/longqt.htm (263 words)

	Long QT Syndrome EKG Analysis
		The defining characteristic of a person with long QT syndrome is that they demonstrate a prolonged QT interval on their EKG.
		The QT interval is the time in milliseconds (ms) between the start of the QRS complex and the end of the T wave where it intersects the isoelectric point.
		Having measured the QT interval, the RR interval is established by measuring the time interval between the QRS peaks of two adjacent heartbeats.
	www.long-qt-syndrome.com /ekg_readout.html (649 words)

	QT interval/questions
		QT is the actual interval at the heart rate you had during the recording of the interval.
		The thing to remember is that QTc is meant to translate the QT interval from what was measured at your heart rate during the test to what the interval would be if your heart rate was actually 60.
		Connie, flecainide can prolong the qt interval and lead to torsades that is why its use is almost always initiated in a hospital for a few days, that could have contributed to your Qt interval being prolonged.
	www.medhelp.org /forums/cardio/messages/35253.html (2680 words)

	Prolonged QT Interval and SIDS
		Prolonged QT interval is a condition where the time between contraction of the heart muscle (Q wave) and 'repolarization' of the heart muscle cells (T wave) is increased.
		Prolonged QT interval syndrome is when the heart takes a longer time to 'repolarize' the heart cells after a contraction than normal.
		ECG's are routinely interpreted by a cardiologist, and evaluation of the QT interval is a routine part of the interpretation.
	sids-network.org /experts/qt.htm (2132 words)

	Guidance for Industry: E14 Clinical Evaluation of QT/QTc Interval Prolongation and Proarrhythmic Potential for
		The QT interval represents the duration of ventricular depolarization and subsequent repolarization, and is measured from the beginning of the QRS complex to the end of the T wave.
		While the degree of QT prolongation is recognized as an imperfect biomarker for proarrhythmic risk, in general there is a qualitative relationship between QT prolongation and the risk of TdP, especially for drugs that cause substantial prolongation of the QT interval.
		As the QT/QTc interval is subject to considerable fluctuation, a possible role for QT/QTc interval prolongation should not be dismissed on the basis of normal on-therapy ECG measurements performed prior to, or near the time of the adverse event.
	www.fda.gov /cder/guidance/6922fnl.htm (6186 words)

	Long QT syndrome - Wikipedia, the free encyclopedia
		The long QT syndrome (LQTS) is a heart disease in which there is an abnormally long delay between the electrical excitation (or depolarization) and relaxation (repolarization) of the ventricles of the heart.
		The QT interval is measured from the Q point to the end of the T wave.
		The syndrome is characterized by Long QT syndrome with ventricular arrhythmias, periodic paralysis and skeletal developmental abnormalities as clinodactyly, low-set ears and micrognathia.
	en.wikipedia.org /wiki/Long_QT_syndrome (2262 words)

	Long QT interval
		The ECG effects of TCA administration include an increase in heart rate (20-25%), prolongation of the PR interval (5-10% increase), increase in QRS duration (7-25%), and prolongation of the QT interval (3-10%).
		The common feature of these conditions is delayed repolarization of the myocardium (related to abnormal sodium or potassium currents) with resultant prolongation of the QT interval of the ECG.
		Adverse effects have occurred when the P450 system is inhibited, leading to elevated levels of medications which prolong the QT interval and produce ventricular tachycardia (torsade de pointes).
	www.scuba-doc.com /longQT.html (788 words)

	BioMed Central \| Full text \| QT interval prolongation after sertraline overdose: a case report
		This is an important side effect since prolongation of the QT interval is strongly associated with life-threatening arrhythmias, most notably torsades de pointes.
		An acquired cause of QT prolongation was suspected since QT intervals had been normal on admission, about 3 hours after ingestion of 2250 mg of sertraline (11 times the maximum maximum recommended dose of 200 mg/day), and were markedly prolonged after one day in hospital.
		We are aware of 1 additional report by Amin et al [11] who described 'a clinically significant' increase in QT interval after treatment with 200 mg of sertraline, however the magnitude of QT prolongation was not specified.
	www.biomedcentral.com /1471-227X/5/5 (1256 words)

	QTsyndrome.ch - Frequently Asked Questions (FAQ)
		The name of the long QT syndrome refers to the QT-interval measured on the electrocardiogram (ECG or EKG for the German term "Elektrokardiogramm").
		The reason is that the QT interval is affected by the heart rate.
		The 9-month interval during pregnancy and the delivery itself are not associated with an increased occurrence of heart events in any of the LQTS women.
	www.qtsyndrome.ch /faq.html (2031 words)

	Long QT interval (Site not responding. Last check: 2007-10-19)
		The QT interval normally varies with heart rate - becoming shorter at faster rates.
		It is usually corrected using the cycle length (R-R interval) as shown opposite.
		Romano-Ward syndrome is an autosomal dominantly inherited form of long QT interval and there is a risk of recurrent ventricular tachycardia, particularly Torsade de Pointes.
	www.ecglibrary.com /l_qt.html (89 words)

	QTsyndrome.ch - To Spread The Word Of Long-QT Syndrome
		In a study of hospitalized injection drug users, QT interval prolongation was seen in a considerable number of patients treated with methadone but not among those not treated with methadone.
		In the epinephrine QT stress test, a patient is medicated to stimulate the heart in such a way that it mimics exercise revealing concealed long QT syndrome.
		QT Kanga is on a worldwide journey to visit several hundred long QT syndrome sufferers.
	www.qtsyndrome.ch (2997 words)

	Long QT syndrome
		The interval between the start of the Q wave and the end of the T wave (QT interval) corresponds to the time it takes for your heart's ventricles to contract and then refill before beginning the next contraction.
		In some people with long QT syndrome, fainting spells are triggered by sudden bursts of adrenaline in the body, such as are experienced during intense exercise or emotional upset.
		In inherited long QT syndrome, the heart may be likened to a "ticking time bomb" and it's largely unknown whether the "bomb" is a dud or about ready to detonate with just the right (or wrong) trigger.
	www.cnn.com /HEALTH/library/DS/00434.html (2979 words)

	Influence of Dofetilide on QT-Interval Duration and Dispersion at Various Heart Rates During Exercise in Humans -- ...
		The QT interval was measured from the onset of the
		predetermined RR intervals of 1000, 900, 800, 700, 600, 500,
		QT dispersion: an indication of antiarrhythmic risk in patients with long QT intervals.
	circ.ahajournals.org /cgi/content/full/94/7/1592 (4071 words)

	Kara Mia: Chapter 12: Long QT Syndrome
		Long QT syndrome is one of the causes of sudden death in adolescents and young adults.
		The majority of the QT interval is the time during a single heartbeat when the heart muscle is becoming "recharged" for the next heartbeat.
		The ion channels are essential to the coordinated contraction of the heart muscle and mutations associated with Long QT syndrome produce a delay in the QT interval- the "recharging" phase of the ECG.
	home.gwi.net /seahorsepress/lqtkara2.htm (925 words)

	QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ...
		QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ankle brachial pressure index and autonomic function tests -- Rana et al.
		QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ankle brachial pressure index and autonomic function tests
		QT interval dispersion for identification of total mortality risk in non-insulin dependent diabetes mellitus.
	heart.bmjjournals.com /cgi/content/full/91/1/44 (4576 words)

	Pharmacy Times: Drug Interactions and QT Interval Prolongation
		In the absence of delayed ventricular conduction, delayed ventricular repolarization usually is identified by the presence of a prolonged QT interval on the electrocardiogram (ECG).
		Prolonged QT intervals can result in premature ventricular complexes that can lead to syncope, dizziness, palpitations, ventricular tachycardia, and sudden death—or they can be asymptomatic.
		Patients with preexisting QT prolongation or a prior history of long-QT syndromes are probably at increased risk of developing arrhythmias and require careful ECG monitoring.
	www.pharmacytimes.com /article.cfm?ID=1785 (630 words)

	SSRI's and prolonged QT interval
		Zoloft can prolong QT interval, more often however if you are on other medications that can prolong QT or if you have a congenital syndrome of prolonged QT interval.
		From what I just read, the QT problem with Zoloft seems to occur when it is used along with Pimozide, and at high doses of 200 mgs.
		Since beta blockers are used to treat prolonged QT interval, one would think it is possible that it shortens the QT interval.
	www.medhelp.org /forums/cardio/messages/34841a.html (1696 words)

	Drug induced QT prolongation and torsades de pointes -- Yap and Camm 89 (11): 1363 -- Heart
		Note the typical short-long-short initiating ventricular cycle, pause dependent QT prolongation, and abnormal TU wave leading to the classical "twisting of a point" of the cardiac axis during TdP.
		The QT interval is influenced by heart rate.
		ECG for excessive increases in the QT interval.
	heart.bmj.com /cgi/content/full/89/11/1363 (4611 words)

	JAMA -- Abstract: What Clinicians Should Know About the QT Interval, April 23, 2003, Al-Khatib et al. 289 (16): 2120
		QT interval and the effect of different methods of measurement
		Development of torsade de pointes caused by exacerbation of QT prolongation during clipping of cerebral artery aneurysm in a patient with subarachnoid haemorrhage
		QT and QTc Interval With Standard and Supratherapeutic Doses of Darifenacin, a Muscarinic M3 Selective Receptor Antagonist for the Treatment of Overactive Bladder
	jama.ama-assn.org /cgi/content/abstract/289/16/2120 (579 words)

	ICH; Guidance for Industry: E14 Clinical Evaluation of QT/QTc Interval Prolongation and Proarrhythmic Potential for ...
		If supported by the QT/QTc interval data from the early clinical studies, later clinical trials could expand the eligibility criteria to include a broader spectrum of patients who are likely to receive the drug once approved.
		The available postmarketing adverse event data should be examined for evidence of QT/QTc interval prolongation and TdP and for adverse events possibly related to QT/QTc interval prolongation, such as cardiac arrest, sudden cardiac death and ventricular arrhythmias (e.g., ventricular tachycardia and ventricular fibrillation).
		This guidance was developed within the Expert Working Group (Efficacy) of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) and has been subject to consultation by the regulatory parties, in accordance with the ICH process.
	www.fda.gov /cber/gdlns/iche14qtc.htm (6088 words)

	QT Interval
		QT is longer in leads V2 and v3
		115 - 84 bpm: QT 0.30 to 0.37 seconds
		83 - 72 bpm: QT 0.32 to 0.40 seconds
	www.fpnotebook.com /CV62.htm (190 words)

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