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Assessing risk of a prolonged QT interval-a survey of emergency physicians.

Chan AS, Isbister GK, Kirkpatrick CM, Duffull SB - Int J Emerg Med (2008)

Bottom Line: These distributions were compared to predicted distributions based on Bazett's corrected QT > 500 ms and the QT nomogram.In four of the six sets of ECG parameters, EPs had a similar risk distribution to that predicted by Bazett.For one point predicted to be high risk by the QT nomogram, there was a uniform (undecided) risk distribution by EPs.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, University of Queensland, Brisbane, Australia.

ABSTRACT

Background: Although QT prolongation is associated with an increased risk of torsades de pointes (TdP), it is unclear how clinicians determine risk in individual patients with prolonged QT.

Aims: To investigate physicians' interpretation of electrocardiogram (ECG) values in patients with a prolonged QT in reference to risk of TdP.

Methods: A survey was sent to Australasian emergency physicians (EPs) to investigate interpretation of ECG data in risk assessment for TdP. The survey contained three sections: demographic information, questions on heart rate correction and six sets of ECG data which the clinician ranked from low to high risk. Risk analysis for ECG values was performed by producing histograms of the distribution of responses for each of the six sets of ECG parameters. These distributions were compared to predicted distributions based on Bazett's corrected QT > 500 ms and the QT nomogram. The QT nomogram is a recently developed method for assessing whether QT-HR pairs are associated with increased risk of TdP by plotting them to determine if they are above an at risk line-the nomogram.

Results: Of 720 surveys sent out, 249 were returned (35%). A heart rate correction was used by 90% of respondents and the median "at risk" QTc judged by EPs was 450 ms [interquartile range (IQR): 440-500 ms]. Respondents were divided as to whether bradycardia increased the risk of TdP, with equal numbers responding "no change" and "more caution". In four of the six sets of ECG parameters, EPs had a similar risk distribution to that predicted by Bazett. For one point predicted to be high risk by the QT nomogram, there was a uniform (undecided) risk distribution by EPs.

Conclusions: EPs mainly relied on Bazett's correction as their method of TdP risk assessment, which may be problematic for bradycardic patients.

No MeSH data available.


Related in: MedlinePlus

Predicted responses for the  distribution, Bazett’s correction factor and the QT nomogram compared to the observed distribution of responses
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Fig2: Predicted responses for the distribution, Bazett’s correction factor and the QT nomogram compared to the observed distribution of responses

Mentions: Parts one and two were summarized using descriptive statistics. For part three, histograms of the distribution of responses (low to high risk) were produced for each set of ECG values. These plots of response distributions were compared to predicted distributions (see Fig. 2): the distribution (where every point was given uniform risk weighting), a risk weighting according to Bazett’s formula and a risk weighting according to the QT nomogram line [7]. The distribution assumed that the physician response to the risk for each QT-HR combination was uniform from low risk (1) to high risk (5). The distribution according to Bazett’s correction formula was created by using QTc=440 ms and QTc=500 ms as cut-off values. QTc values of more than 500 ms were given a high risk rating, those falling between 440 and 500 were medium risk and those values less than 440 were considered low risk. The QT nomogram line was used to predict the last set of responses. Values of QT-HR falling above the line were considered high risk, those on the line were given medium risk and the values which fell below the line were considered low risk. A visual analysis between the distribution of the survey results and the predicted distributions was then performed.Fig. 2


Assessing risk of a prolonged QT interval-a survey of emergency physicians.

Chan AS, Isbister GK, Kirkpatrick CM, Duffull SB - Int J Emerg Med (2008)

Predicted responses for the  distribution, Bazett’s correction factor and the QT nomogram compared to the observed distribution of responses
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2536188&req=5

Fig2: Predicted responses for the distribution, Bazett’s correction factor and the QT nomogram compared to the observed distribution of responses
Mentions: Parts one and two were summarized using descriptive statistics. For part three, histograms of the distribution of responses (low to high risk) were produced for each set of ECG values. These plots of response distributions were compared to predicted distributions (see Fig. 2): the distribution (where every point was given uniform risk weighting), a risk weighting according to Bazett’s formula and a risk weighting according to the QT nomogram line [7]. The distribution assumed that the physician response to the risk for each QT-HR combination was uniform from low risk (1) to high risk (5). The distribution according to Bazett’s correction formula was created by using QTc=440 ms and QTc=500 ms as cut-off values. QTc values of more than 500 ms were given a high risk rating, those falling between 440 and 500 were medium risk and those values less than 440 were considered low risk. The QT nomogram line was used to predict the last set of responses. Values of QT-HR falling above the line were considered high risk, those on the line were given medium risk and the values which fell below the line were considered low risk. A visual analysis between the distribution of the survey results and the predicted distributions was then performed.Fig. 2

Bottom Line: These distributions were compared to predicted distributions based on Bazett's corrected QT > 500 ms and the QT nomogram.In four of the six sets of ECG parameters, EPs had a similar risk distribution to that predicted by Bazett.For one point predicted to be high risk by the QT nomogram, there was a uniform (undecided) risk distribution by EPs.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy, University of Queensland, Brisbane, Australia.

ABSTRACT

Background: Although QT prolongation is associated with an increased risk of torsades de pointes (TdP), it is unclear how clinicians determine risk in individual patients with prolonged QT.

Aims: To investigate physicians' interpretation of electrocardiogram (ECG) values in patients with a prolonged QT in reference to risk of TdP.

Methods: A survey was sent to Australasian emergency physicians (EPs) to investigate interpretation of ECG data in risk assessment for TdP. The survey contained three sections: demographic information, questions on heart rate correction and six sets of ECG data which the clinician ranked from low to high risk. Risk analysis for ECG values was performed by producing histograms of the distribution of responses for each of the six sets of ECG parameters. These distributions were compared to predicted distributions based on Bazett's corrected QT > 500 ms and the QT nomogram. The QT nomogram is a recently developed method for assessing whether QT-HR pairs are associated with increased risk of TdP by plotting them to determine if they are above an at risk line-the nomogram.

Results: Of 720 surveys sent out, 249 were returned (35%). A heart rate correction was used by 90% of respondents and the median "at risk" QTc judged by EPs was 450 ms [interquartile range (IQR): 440-500 ms]. Respondents were divided as to whether bradycardia increased the risk of TdP, with equal numbers responding "no change" and "more caution". In four of the six sets of ECG parameters, EPs had a similar risk distribution to that predicted by Bazett. For one point predicted to be high risk by the QT nomogram, there was a uniform (undecided) risk distribution by EPs.

Conclusions: EPs mainly relied on Bazett's correction as their method of TdP risk assessment, which may be problematic for bradycardic patients.

No MeSH data available.


Related in: MedlinePlus