(redirected from QRS interval)
Also found in: Dictionary, Thesaurus, Medical, Legal.
Related to QRS interval: QT interval


in music, the difference in pitch between two tones. Intervals may be measured acoustically in terms of their vibration numbers. They are more generally named according to the number of steps they contain in the diatonic scale of the piano; e.g., from C to D is a second, C and D being the first two notes of the scale of C. The fourth, fifth, and octave are termed perfect intervals as they have a characteristic sonority quite unlike any other interval. An interval between two natural notes, neither note being a sharp or a flat, is a major interval; if it is reduced by a semitone, it becomes minor. If a perfect or a minor interval is made half a step smaller it is called diminished, and when half a step larger, augmented. An interval may also be expressed by means of the ratio of the frequencies of its two tones. For example, the octave may be expressed by the ratio 2:1 because its upper tone has a frequency twice that of its lower tone.



in music and acoustics, the correlation of two tones according to pitch, that is, the frequency of sound vibration. The lower tone of an interval is known as its foundation, the upper its top. Tones employed in succession form a melodic interval; when used simultaneously, a harmonic interval. Each interval is determined by the volume, or quantitative, magnitude—that is, the number of steps it comprises—and the tonal, or qualitative, magnitude—that is, the number of whole tones or semitones it contains. Intervals formed within the limits of an octave are called simple intervals, and larger ones are called compound intervals. The names of intervals indicate the number of steps each embraces: the tonal size of the intervals determines whether they are minor, major, perfect, augmented, or diminished.

The simple intervals are perfect unison, minor second (a half tone), major second (one tone), minor third (1½ tones), major third (two tones), perfect fourth (2½ tones), augmented fourth (three tones), diminished fifth (three tones), perfect fifth (3½ tones), minor sixth (four tones), major sixth (4½tones), minor seventh (five tones), major seventh (5½tones), and perfect octave (six tones).

Compound intervals are created by adding a simple interval to the octave. They retain the characteristics of the analogous simple intervals; thus, there are ninths, tenths, elevenths, twelfths, thirteenths, fourteenths, and fifteenths (two octaves). Wider intervals are called a second above (or below) two octaves, a third above two octaves, and so on.

The enumerated intervals are known also as fundamental, or diatonic, intervals. Diatonic intervals can be increased or diminished by raising or lowering the foundation or top of the interval one chromatic semitone. If, simultaneously, both steps of an interval are subjected to alteration by a chromatic semitone in different directions, a double-augmented interval results; if one step is altered by one chromatic tone a double-diminished interval is produced. All intervals changed through alteration are called chromatic intervals. Intervals that differ in the quantity of steps they contain but are alike in tonal makeup (sound) are considered enharmonically equal—for example, F to G sharp (an augmented second) and F to A flat (a minor third).

All harmonic intervals are divided into consonant and dissonant intervals. The consonant intervals are the perfect unison and the octave (perfect consonance), the perfect fourth and the perfect fifth (very good consonance), and minor and major thirds and sixths (imperfect consonance). The dissonant intervals are minor and major seconds, the augmented fourth, the diminished fifth, and minor and major sevenths. The transference of the tones of an interval, during which the foundation becomes the upper tone of the interval and the top its lower tone, is called inversion; a new interval results. In inversion all perfect intervals remain perfect, minor intervals become major, major become minor, augmented become diminished, diminished become augmented, double augmented become double diminished, and double diminished become double augmented.



The spacing in pitch or frequency between two sounds; the frequency interval is the ratio of the frequencies or the logarithm of this ratio.
A set of numbers which consists of those numbers that are greater than one fixed number and less than another, and that may also include one or both of the end numbers.
The time separating two events, or the distance between two objects.
In special relativity, the Lorentz invariant quantity c 2t)2-(Δ x)2-(Δ y)2-(Δ z)2, where c is the speed of light, Δ t is the difference in the time coordinates of two specified events, and Δ x, Δ y, and Δ z are differences in their x, y, and z coordinates, respectively.
In general relativity, a generalization of this concept, namely the sum over the indices μ and ν of gμν dx μ dx ν, where dx μand dx νare the differences in the x μand x νcoordinates of two specified neighboring events, and gμνis an element of the metric tensor.


1. Music the difference of pitch between two notes, either sounded simultaneously (harmonic interval) or in succession as in a musical part (melodic interval). An interval is calculated by counting the (inclusive) number of notes of the diatonic scale between the two notes
2. the ratio of the frequencies of two sounds
3. Maths the set containing all real numbers or points between two given numbers or points, called the endpoints. A closed interval includes the endpoints, but an open interval does not
References in periodicals archive ?
OBJECTIVE: We evaluated the association between a history of arsenic exposure from drinking water and the prolongation of heart rate-corrected QT (QTc), PR, and QRS intervals.
It was this approach that led the Centers for Medicare and Medicaid Services to restrict reimbursement to the subgroup of patients with a prolonged QRS interval.
The Centers for Medicare and Medicaid Services recently removed several exclusions for ICD coverage, including those for patients with high QRS intervals, or left ventricular ejection fractions of 30%-35% (INTERNAL MEDICINE NEWS, Feb.
In light of biologic probability that QRS interval may be a limiting factor in the benefit of defibrillators, it was not imprudent to await more data before approving coverage of an expensive technology in that group, he said.
He participated in a panel discussion on CMS coverage and reimbursement issues in which he heard complaints by physicians who said they felt sickened by having to tell heart failure patients that, although an ICD might be life-saving for them, Medicare won't pay for it because their QRS interval isn't long enough.
But when CMS announced its coverage decision in June, it declared that the government agency would pay for ICDs only in the roughly one-third of MADIT II-type patients having a QRS interval greater than 120 milliseconds.
Some have suggested that there may be a greater benefit for patients with a wider QRS interval, but that is only a hypothesis that should not be acted upon without more evidence.
The study enrolled patients with New York Heart Association class III or IV heart failure who had a left ventricular ejection fraction of 35% or less, a QRS interval of at least 120 msec, and a PR interval above 150 msec.
Ventricular pacemakers placed in the left and right ventricles in patients with bundle branch block and a QRS interval greater than 140 milliseconds have been shown to reorganize that ventricular contractility.
Having possibility to measure of RR, JT and QRS intervals complexity with help of Hankel matrix rank, it's possible to represent different clinical situations with complexity profile, where the largest scale is RR interval, middle scale is JT interval and smallest scale is QRS duration.
Measurement of the QT interval should be as critical as measurement of the PR and QRS intervals.