Hemodynamic effects of cardiac arrhythmias

Left ventricular function during stable sustained ventricular tachycardia. Hemodynamic and echo-Doppler analysis

To assess the left ventricular function during sustained stable ventricular tachycardia (VT), ten patients, aged 58 to 74, underwent simultaneous echo-Doppler and hemodynamic studies during sinus rhythm and induced sustained stable monomorphic VT. The VT cycle length was 447 +/- 92 ms (mean +/- SD). During VT, cardiac index fell from 2.32 +/- 0.54 to 1.62 +/- 0.63 L/min/m2 (p less than 0.001), and systemic systolic blood pressure fell from 129 +/- 18 to 107 +/- 18 mm Hg (p less than 0.001), while left ventricular end-diastolic pressure showed a rising trend from 9 +/- 7 to 15 +/- 12 mm Hg, and pulmonary artery wedge pressure rose from 10.2 +/- 1.6 to 24.2 +/- 2.3 mm Hg (p less than 0.005). By echo-Doppler the ejection fraction and the presence and degree of valvular regurgitation were not significantly changed during VT. The mean maximal left ventricular inflow tract velocities, mean time velocity integrals, and the mean time velocity integrals normalized for heart rate (measures of left ventricular diastolic filling) decreased from 0.59 +/- 0.074 to 0.40 +/- 0.053 m/s (p less than 0.05), from 0.12 +/- 0.029 to 0.021 +/- 0.012 m (p less than 0.001), and from 7.43 +/- 1.20 to 3.21 +/- 1.49 m x beats/min (p less than 0.001) during VT, respectively. We conclude that hemodynamic changes during stable sustained VT are neither associated with significant changes in systolic left ventricular function nor related to valvular regurgitation and are likely caused by impaired left ventricular diastolic filling.

Relation between premature ventricular contraction site of origin (defined by radionuclide phase analysis) and subsequent left ventricular function

It has been suggested that the effect of a premature ventricular contraction (PVC) on left ventricular (LV) function depends on the site of origin of the PVC, and that the subsequent impairment of LV performance during a PVC may be more pronounced if baseline LV dysfunction is present. To evaluate these concepts, radionuclide angiographic phase image analysis of spontaneous PVCs was performed after acquisition of images from PVCs alone by a new gating procedure. The sites of the PVCs were localized to 1 of 3 right ventricular (RV) or 5 left ventricular (LV) regions by this method. LV function during PVCs was assessed and compared with baseline by noting the LV ejection fraction (EF) during PVCs, the difference between sinus LVEF and PVC EF, and the normalized PVC EF (PVC EF/sinus EF). Twenty-four patients had LV PVC sites and 19 had RV sites. LV function during a PVC appeared to be independent of either the ventricle of origin of the PVC or a specific site of origin within the ventricles. The resultant PVC ventricular function also appeared independent of sinus LVEF and sinus wall motion abnormalities. In addition, no correlation between coupling interval and any of the variables measured was demonstrated (although extremely short coupling intervals were not evaluated). These data suggest that the effects of PVCs on ventricular performance seen during ventricular ectopy are independent of the site of origin of the PVC, baseline wall motion abnormalities or PVC coupling interval in the population studied.

Two-dimensional echocardiographic studies during sustained ventricular tachycardia

We evaluated left ventricular function in patients with recurrent sustained ventricular tachycardia (VT) using two-dimensional echocardiography (2DE). Thirteen patients, 11 men and 2 women, age range 42-77 (mean 62 +/- 12) years were studied in sinus rhythm (SR) and immediately after VT induction. 2DE parameters analyzed included wall motion, mitral valve leaflet motion, and ejection fraction (EF). In SR, 21 segments/walls in 12 patients showed wall motion abnormalities (WMA) ranging from hypokinesis to dyskinesis and one patient had generalized LV hypokinesis. In VT, new WMA were noted in 2 patients. Thirteen segments/walls in 8 patients showed further worsening of pre-existing WMA. In 1 patient there was worsening of generalized LV hypokinesis. Three patients showed apparent improvement in pre-existing WMA during VT. In 2 patients large apical aneurysms showed a reduction of dyskinesis in VT. Mitral valve opening was intermittent in patients with shorter VT cycle lengths and was maximal when atrial systole preceded or coincided with ventricular depolarization. Doppler echocardiography in 1 patient confirmed the pattern of intermittent mitral flow, with greatest flow occurring when mitral valve opening occurred well before the QRS peak. In 5 patients, 2DE permitted EF measurements. EF in SR ranged from 24-56% (mean 36 +/- 13), decreased to 6-33% (mean 21 +/- 11) within the first ten beats of VT and 6-25% (mean 19 +/- 8) after twenty beats of VT. EF decreased more in patients with shorter VT cycles as compared to those with longer VT cycle lengths.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of left ventricular mechanical function during arrhythmias by two-dimensional echocardiography. II. Location of the site of onset of premature ventricular systoles

Two-dimensional echocardiography was applied experimentally in a closed chest dog model with intact pericardium to determine the location, magnitude and extent of contractile response during pacing from discrete ventricular sites. Midventricular short-axis tomographic images obtained during regular sinus rhythm and subsequent premature ventricular beats provided comparative measurements of global and segmental systolic changes of cross-sectional luminal areas and myocardial wall thickness. Computer-assisted standardized analysis of segmental systolic fractional area change and wall thickening was used to map left ventricular contraction during normal rhythm and premature beats of 70% coupling interval, induced alternately from anterior and lateral aspects of the mid-left ventricular short-axis cross-sectional plane. A characteristic pattern consisting of early systolic contraction and wall thickening was followed by paradoxical motion and wall thinning in late systole in segments corresponding to the region of direct electrical stimulation. Statistical analysis of segment by segment function indicated a maximal amount of premature beat contractile derangement at the site of the stimuli. Pacing from a right ventricular wall site in the midventricular plane caused a similar premature beat response at the anterior aspect of the interventricular septum. It is concluded that two-dimensional echographic analysis of segmental ventricular function can identify the location of electrical stimuli, and thus might noninvasively characterize regional patterns of contraction associated with ectopic foci during arrhythmias.

Characterization of left ventricular mechanical function during arrhythmias with two dimensional echocardiography. I. Premature ventricular contractions

Two dimensional echocardiography was applied experimentally in the closed chest dog to quantitate left ventricular function during and immediately after single premature ventricular contractions induced through threshold stimulation at the apex. Coupling intervals were varied over a range from 35 to 85 percent of the R-R interval during normal sinus rhythm (920 to 980 ms). The quality of tomographic echocardiographic images during premature as well as postextrasystolic beats was found to be satisfactory for quantitating short axis section areas at end-diastole and end-systole. A systolic fractional area change was computed from two dimensional echocardiographic measurements to characterize mid ventricular cardiac function, which correlated significantly with peak left ventricular pressure and maximal first derivative of left ventricular pressure (dP/dt). Marked shortening of coupling intervals reduced fractional shortening during premature systole and enhanced the degree of potentiation during the postextrasystolic beat. By contrast, premature beats with relatively long coupling intervals caused less reduction in contraction and only minor postextrasystolic potentiation. Systolic shortening of left ventricular length as well as transverse diameters were studied in a two dimensional echocardiographic long axis cross section. During long coupling intervals contraction was normal except for distinct regional systolic outward "bulging" in the apical region. In contrast, short coupling intervals were associated with a more significant generalized derangement of ventricular wall motion during systole. It is concluded that the two dimensional echocardiographic method can be used to portray and quantitate global as well as regional left ventricular function during disturbances of cardiac rhythm.

Echocardiography in assessing mitral valve motion in 3 horses with atrial fibrillation

Echocardiography is a non-invasive, safe means of assessing intracardiac structures and their motion. In the normal motion of the mitral valve there is anterior motion noted during atrial systole. In 3 horses with atrial fibrillation the mitral valve motion had no anterior motion to correspond with atrial contractions. Quinidine returned the electrocardiogram of one horse to a sinus rhythm after which echocardiography demonstrated the reappearance of the anterior motion of the mitral valve.

Arrhythmias and conduction disturbances following aortic valve implantation

In the first postoperative week following aortic valve implantation, arrhythmias and conduction disturbances were seen in 37 of 44 patients studied. Sixty-seven episodes of arrhythmias occurred, atrial fibrillation and accelerated junctional rhythms accounted for more than 75% of these episodes. Episodes of atrial fibrillation were most common after the age of sixty.l When atrial premature contractions were observed, episodes of atrial fibrillation followed shortly afterwards. Accelerated junctional rhythms were seen in 17 patients and affected the patients haemodynamically when this dysrhythmia occurred early in the postoperative course, but improvements were seen promptly following atrial overpacing. Lidocaine was infused prophylactically for 2 days in patients with severe aortic stenosis or marked left ventricular hypertrophy. One episode of ventricular fibrillation and few incidents of ventricular extrasystoles were seen. Most conduction disturbances were transient, but bundle branch block persisted in 3 patients, and there was complete A-V block in a fourth. No causal relationship between the use of digitoxin and the frequency of arrhythmias could be established.

A simple method for correcting left ventricular equilibrium radionuclide angiography for the effects of arrhythmias

A simple method of correcting equilibrium radionuclide angiographic data for the effects of arrhythmias is proposed. This involves no further acquisition time or inconvenience to the patient. This correction is necessary in patients with marked arrhythmias as the left ventricular time-activity curve (LVTAC) becomes distorted with greater sampling time in the first few frames of the LVTAC than in later frames. This will show on the LVTAC as greater counts in the first few frames and will lead to an overestimation of left ventricular ejection fraction (LVEF) and wall motion. The method proposed normalises each frame to make the contribution from a non-cardiac region constant over the cardiac cycle. Results of the correction are presented and discussed.