Interpretation of cardiac pathophysiology from pressure waveform analysis: effects of nitroglycerin.

Nitroglycerin has dependable, short-lived veno- and arterial vasodilatory effects ameliorating ischemia through both preload reduction and coronary vasodilation. Nitroglycerin should be used prior to left ventriculography in patients with elevated left ventricular end-diastolic pressure. The arterial pressure waveform alteration of nitroglycerin can be explained on the basis of changes in arterial distensibility and reflected wave patterns and may vary considerably among individuals with different degrees of atherosclerosis.     

Interpretation of cardiac pathophysiology from pressure waveform analysis: cardiac arrhythmias.

Various arrhythmias can produce distorted pressure waveforms, which may be confused with benign physiologic events. Delay in the management of serious arrhythmias can be avoided by vigilant monitoring of systemic pressures.     

Interpretation of cardiac pathophysiology from pressure waveform analysis: Coronary hemodynamics: I. Coronary catheter pressures

Pressure waveform fidelity was examined in two sizes of the Bard catheter introducer. The purpose of this endeavor was to determine whether accurate blood pressure measurements could be achieved directly via the catheter introducers. The introducers were incorporated into a mock circulatory system for the study. The effects of supporting dilators and catheters within the introducer sheath during pressure measurements were also considered. Parameters used to explain pressure waveform response within the catheter introducers included the damping coefficient and the natural frequency of the catheter introducer, and the effects of impedance mismatching between the transducer and the mock circulatory system. Overall, the pressure measurements obtained from the catheter introducer were distorted. Mean pressure levels measured in the introducers were up to 15 mmHg higher than the true mean pressure. The distortion in the pressure measurements can be attributed for the most part to impedance mismatching. In sum, the pressure measurements obtained from catheter introducer-manometer systems should be used only referentially, and not as an absolute standard.     

Interpretation of cardiac pathophysiology from pressure waveform analysis: the pulmonary valve.

Although an uncommon lesion, when pulmonary stenosis is considered, pulmonary artery and right ventricular pressures should be assessed simultaneously on two-catheter pullback to appreciate the precise location of pulmonary-right ventricular pressure gradients. The case examples demonstrate that the peripheral pulmonic stenosis can mimic pulmonary valve stenosis and that pulmonary artery insufficiency may be difficult to delineate on pressure alone (as is often the case with the hemodynamics of aortic insufficiency). These hemodynamic tracings are complemented by the echocardiographic and angiographic characterization of pulmonic valve lesions. Conduction defects or ventricular hypertrophy can affect the right ventricular pressure tracing and either delay or increase the timing of pressure rise and decline depending on the conduction disturbance and abnormality of myocardial contraction.     

Interpretation of cardiac pathophysiology from pressure waveform analysis: the left-sided V wave

The left-sided V wave is dependent on both left atrial and ventricular pressure/volume filling relationship. The cardiac rhythm and timing of atrial systole also influences the V wave. The morphology of the V wave can reflect the severity of mitral regurgitation with stenosis, but valve areas in this setting may be better assessed by a pressure half-time method. Finally, as queried in our first patient example, V wave alternans is a reflection of left ventricular pressure alternans in a failing heart. Other signs of poor left ventricular function in Figure 1 also included an elevated minimal diastolic pressure and markedly elevated left ventricular end diastolic pressure. Hemodynamic findings of poor left ventricular function will be addressed in detail in a later "Rounds."     

Interpretation of cardiac pathophysiology from pressure waveform analysis: percutaneous balloon valvuloplasty.

The hemodynamic findings of aortic, mitral and pulmonary balloon valvuloplasty serve to identify classical valvular lesions and their responses to graded or abrupt catheter dilation techniques. The production of mild insufficiency after valve dilation is generally well tolerated. Severe valvular insufficiency produces the expected hemodynamic alterations, but acute decompensation may be witnessed over brief periods of time. The use of extra stiff guidewires across dilated valves, especially the aortic valve, may also produce an exaggerated hemodynamic picture of insufficiency. Although gradients may be reduced, the effect of valve dilation on aortic valve area is generally small. A discussion of factors influencing valve area calculations will be the subject of a future "Rounds."