Effect of Pacing on Aortic dP/dt Values
Condition: Aortic Diseases
MeSH terms: Aortic Diseases
Study type: Interventional

Summary: 
      The maximum value of rate of left ventricular pressure increase, denoted by left ventricular
      peak dP/dt value (dP/dt max), corresponds to the highest point on the curve of first
      derivative of ventricular pressure curve with respect to time. It is one of the important
      systolic performance parameters, which is primarily determined by ventricular contractility,
      and emerges in isovolumetric contraction phase when aortic valves are closed. Thus it is not
      influenced by parameters beyond ventricle such as aortic valve area, aortic elastance and
      peripheral resistance. Despite these unique advantageous, the main reason for its limited
      usage in assessing ventricular systolic performance instead of commonly used ejection
      fraction is the difficulties in its calculation, which requires incessant intraventricular
      pressure recordings.

      The maximum value of acceleration rate of aortic pressure increase can be named as aortic
      peak dP/dt. It, likewise, corresponds to the maximum value of first derivative of pressure
      curve with respect to time.

      Since it is one of the principal determining factors of aortic peak dP/dt, changing left
      ventricular contractility thereby left ventricular peak dP/dt value is expected to change
      aortic peak dP/dt in the same direction since all other variables being unchanged. Yet to
      conclude the extent of this association and magnitude of change, measuring these parameters
      for various contractility levels is necessary. In addition, impact of decreasing left
      ventricular peak dP/dt by gradually lowering ventricular contractility upon aortic peak dP/dt
      has not been investigated in previous studies.

      In the present study, changes in left ventricular and aortic peak dP/dt values in response to
      gradual reduction in LV contractility with stepwise changing (decremental shortening)
      atrio-ventricular delay (AVD) by dual chamber pacing will be investigated in patients without
      systolic dysfunction.
    

Detailed description: 
      The maximum value of rate of left ventricular pressure increase, denoted by left ventricular
      peak dP/dt value (dP/dt max), corresponds to the highest point on the curve of first
      derivative of ventricular pressure curve with respect to time. It is one of the important
      systolic performance parameters, which is primarily determined by ventricular contractility,
      and emerges in isovolumetric contraction phase when aortic valves are closed. Thus it is not
      influenced by parameters beyond ventricle such as aortic valve area, aortic elastance and
      peripheral resistance. Despite these unique advantageous, the main reason for its limited
      usage in assessing ventricular systolic performance instead of commonly used ejection
      fraction is the difficulties in its calculation, which requires incessant intraventricular
      pressure recordings.

      The maximum value of acceleration rate of aortic pressure increase can be named as aortic
      peak dP/dt. It, likewise, corresponds to the maximum value of first derivative of pressure
      curve with respect to time. Unlike left ventricular peak dP/dt, it emerges after aortic valve
      opens in early systolic ejection phase and thus is influenced by parameters beyond ventricle
      in addition to left ventricular contractility such as aortic elastance and compliance,
      vascular resistance, interference of forward and backward propagating pressure waves, stroke
      volume and its ejection rate (dV/dt). Notably, aortic peak dP/dt can be expected to be one of
      principal determinants in pressure-related damages in the vascular system. In structures
      exposed to variable pressures, the extent of damage depends on the magnitude and rate of
      acceleration of applied pressure in addition to susceptibility of the structures. Whether
      this mechanism, which has numerous implications from the real world, operates in the organism
      as well can be exemplified by the pulse pressure, which is an independent risk factor for
      adverse cardiovascular events apart from systolic and diastolic blood pressure levels. A wide
      pulse pressure suggests an accelerated rate of pressure increase. Therefore applications
      lowering left ventricular and aortic peak dP/dt values may open a new therapeutic avenue in
      management of pressure-related vascular damages such as aortic aneurisms. However, aortic
      peak dP/dt concept is seldom found a place even in research articles.

      Since it is one of the principal determining factors of aortic peak dP/dt, changing left
      ventricular contractility thereby left ventricular peak dP/dt value is expected to change
      aortic peak dP/dt in the same direction since all other variables being unchanged. Yet to
      conclude the extent of this association and magnitude of change, measuring these parameters
      for various contractility levels is necessary. In this context, it has been demonstrated that
      narrowing of the QRS complex by cardiac resynchronization therapy (CRT) was shown to increase
      left ventricular peak dP/dt value. This finding strongly suggests that widening of the QRS
      complex, on the contrary, will decrease left ventricular peak dP/dt value. However, impact of
      decreasing left ventricular peak dP/dt by gradually lowering ventricular contractility upon
      aortic peak dP/dt has not been investigated in previous studies.

      In the present study, changes in left ventricular and aortic peak dP/dt values in response to
      gradual reduction in left ventricular (LV) contractility with stepwise changing (decremental
      shortening) atrio-ventricular delay (AVD) by dual chamber pacing will be investigated in
      patients without LV systolic dysfunction.
    

Intervention name(s): Temporary DDD pacing
Intervention type(s): Device
Intervention description(s): Measurements will be performed in patients otherwise undergoing invasive catheterization procedure. Baseline ventricular and aortic hemodynamic parameters (continuous pressure recordings) will be recorded. Thereafter, DDD pacing with stepwise changing of the AV delay will be performed. During each pacing steps left ventricular and aortic pressures at different aortic levels will be continuously recorded. From these hemodynamic data, left ventricular and aortic dP/dt values will be calculated off line.
Allocation: Non-Randomized
Intervention model: Sequential Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Ventricular contractility; Pacing; Ventricular dP/dt; Aortic dP/dt