Non-Specific Intra-Ventricular Conduction Delay (nsIVCD) - A quick-lit-review.

Non-Specific Intra-Ventricular Conduction Delay (nsIVCD) - A quick-lit-review.

The clinical/prognostic significance of a non-specific intra-ventricular conduction delay - A quick-lit-review.

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Simon Mark

August 16, 2019
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    "nonspecific intraventricular conduction delay is defined by a QRS duration

    >110ms in adults, >90ms in 8-16yr olds and >80ms in under 8 year olds. without meeting the criteria for RBBB or LBBB." DEFINITION AS PER AHA/ACC/HRS (2009); These conduction delays may be observed after large myocardial infarctions, in which the necrotic area may cause non-specific conduction disturbances. Delays may be due to myocardial fibrosis, amyloidosis, cardiomyopathy or hypertrophy. NON-SPECIFIC INTRA-VENTRICULAR CONDUCTION DELAY (nsIVCD).
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    NON-SPECIFIC INTRA-VENTRICULAR CONDUCTION DELAY (nsIVCD). DEFINITION AS PER "LIFE IN

    THE FAST LANE.COM" (2019); QRS interval >120ms; Absence of a supraventricular rhythm. Most commonly this will be due to bundle branch block or hypertrophy. There are a variety of causes for an IVCD, but a non-specific IVCD can only be defined in their absence; . Fascicular (LAFB & LPFB) and bundle branch blocks; Left and right ventricular hypertrophy; Bi-ventricular enlargement; Dilated cardiomyopathy; Wolf Parkinson White syndrome (WPW) (also delta wave); Brugada syndrome; Arrhythmogenic right ventricular dysplasia (ARVD) (also epsilon waves). Hyperkalaemia; Sodium channel blocker toxicity (TCA overdose) (also +ve R wave in aVR). (2 life-threatening causes that should be excluded as a priority).
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    Quick-lit-review for the term "clinical significance of non- specific intra-ventricular

    conduction delay" performed. "Intraventricular Conduction Delay in a Standard 12-Lead Electrocardiogram as a Predictor of Mortality in the General Population." Aro et al (2011). "Prognostic implications of intraventricular conduction delays in a general population: The Health 2000 Survey." Tiosano et al (2016). "Prevalence of ventricular conduction blocks in the resting electrocardiogram in a general population: The Health 2000 Survey." Haataja et al (2016). "Prognostic Significance and Clinical Utility of Intraventricular Conduction Delays on the Preoperative Electrocardiogram." Richardson et al (2018). "A Three-Decade Survival Analysis of Intraventricular Conduction Delay in Adults Without Ischemic Heart Disease." Haataja et al (2014). 5 studies were identified;
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    ARO ET AL (2011); 10,957 Finnish subjects aged 30-60years. Data

    obtained from screening between 1966-1972. Non-specific IVCD (nsIVCD) was associated with increased mortality and a markedly increased risk of sudden arrhythmic death in the general population. This was independent of factors that may be expected to predict cardiac death and risk of sudden arrhythmic death increased 3-fold even after multivariant adjustment. In patients with suspected coronary artery disease (CAD), nsIVCD was an independent predictor of cardiac death and non-fatal myocardial infarction (MI). In patients with suspected acute coronary syndrome (ACS), nsIVCD predicted in-hospital and 1 year mortality. In the general population without BBB, a change in QRS delay from <110ms to >130ms was associated with an 1.8 fold increase in risk of cardiovascular death. In hypertensive patients with left ventricular hypertrophy, nsIVCD predicted all cause and cardiovascular mortality and identified patients at risk of sudden cardiac death.
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    HAATAJA ET AL (2014); 6,299 Finnish subjects. 8 year follow-up.

    In the general population, nsIVCD (as well as left bundle branch block and incomplete right bundle branch block) was associated with increased risk for all cause and cardiovascular mortality.
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    TIOSANO ET AL (2016); 2,465 Isreali subjects between 1976-1982. 30

    year follow-up. When controlled for gender, age and BMI, nsIVD was not associated with increased mortality in individuals without ischaemic heart disease.
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    HAATAJA ET AL (2016); 6,315 Finnish subjects. nsIVCD was associated

    with CAD/angina (22.9% of patients). nsIVCD was associated with heart failure (11.4% of patients).
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    RICHARDSON ET AL (2018); 152,479 non-cardiac surgical patients. Retrospective analysis.

    3.3% of subjects had nsIVCD. ECGs with conduction delays did not confer an increased risk of post-operative death. Risk of post-operative MI was not significantly increased among those with conduction delays, compared with normal ECGs.
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    3 out of 4 studies (including the largest cohort) indicated

    that nsIVCD was a predictor of mortality - cardiac & non- cardiac. CONCLUSIONS; At 30yr follow-up & when adjusted for controls, nsIVCD was not associated with increased mortality in those without IHD. There is no increased surgical risk in individuals with nsIVCD. These apparently contradictory findings can perhaps be reconciled by interpreting that nsIVCD is a predictor of IHD, as well as mortality for those with IHD only. It is more difficult to interpret the significance of nsIVCD in those without IHD, although the largest cohort study found increased mortality and sudden arrhythmic death in the general population with nsIVCD.
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    IMPLICATIONS FOR CLINICIANS; The threshold for testing those at risk

    of IHD/CAD should be lower in those with nsIVCD. Testing threshold Individuals with nsIVCD do not need any specific surgical considerations. Surgery Individuals with nsIVCD but with a proven absence of IHD/CAD may still have greater risk of death therefore appropriate clinical judgement should be applied on a case by case basis. Absence of IHD/CAD Individuals with nsIVCD should have their risk factors aggressively controlled, as the largest cohort study suggests that they are at greater risk of IHD/CAD and sudden death. Risk factors