Download Institutional and national trends in isolated mitral valve surgery over

Institutional and national trends in isolated mitral valve surgery
over the past decade
Niv Ad, Scott D. Barnett, Alan M. Speir and Paul S. Massimiano
Inova Heart and Vascular Institute, Falls Church,
Virginia, USA
Correspondence to Niv Ad, MD, Inova Heart and
Vascular Institute, 3300 Gallows Road, Falls Church,
VA 22042, USA
Tel: +1 703 776 8308; fax: +1 703 776 8303;
e-mail: [email protected]
Current Opinion in Cardiology 2008, 23:99–104
Purpose of review
To review trends in practice for mitral valve surgery in the US over the past decade.
Recent findings
Advances in the understanding of mitral valve pathophysiology and the technology
involved with mitral valve surgery have led to significant changes of the current practice for
mitral valve surgery, with mitral valve repair being the technique of choice. Mitral valve
repair is currently applied to close to 60% of patients having surgery for mitral valve
disease in the US. This trend in the change of practice also contributed to a sharp
decrease in the use of mechanical mitral valve prosthesis even in the younger population.
Summary
Current practice for mitral valve surgery in the US reflects a steady increase in
performed procedures over the last decade. The increased use of mitral valve repair
techniques to address mitral valve disease can be related to increased surgical
experience and greater understanding of the pathophysiology of mitral valve disease as
well as the improved outcome related to mitral valve repair.
Keywords
cardiovascular surgery, mitral valve repair, mitral valve replacement, trends
Curr Opin Cardiol 23:99–104
ß 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
0268-4705
Background
Recent improvements in surgical techniques and understanding of the pathophysiology of mitral valve disease,
together with improved perioperative patient care, have
led to significant changes in the surgical strategies applied
as well as better results following mitral valve surgery
[1,2,3]. These improvements are largely due to the
higher percentage of patients having mitral valve repair
rather than replacement. Recent work has demonstrated
that, when compared with mitral valve replacement, mitral
valve repair patients experience decreased length of stay
and in-hospital mortality, equivalent quality of life, and
increased long-term survival [4–6]. The significance of
the changes is directly related to recent reports regarding
the increasing age of the US population [7] combined
with expected increases in cardiovascular disease [8],
suggesting the total number of mitral valve procedures
will increase in a potentially more complex population.
Here, we detail changes in North America as well as in our
practice for mitral valve surgery strategies over the past
decade.
between 1996 and 2005 in North America and 1996 and
2006 for our institute. Primary endpoints considered were
mitral valve trends, length of stay (LOS) and operative
death. Trends were examined for gender, age (65 years or
younger, or over 65 years) and implant type (bioprosthesis, mechanical or repair) categories.
National mitral valve surgery estimates
National data for mitral valve surgery during the years
1996 through the most recent year (2005) were obtained
through the Healthcare Cost and Utilization Project
(HCUP), Agency for Healthcare Research and Quality,
National Inpatient Sample (NIS). The NIS is the largest
publicly available all-payer inpatient care database available within the US, representing a 20% national sample
consisting of 5–8 million hospital stays from 1000 participating hospitals [9]. As the NIS lists up to 15 International Statistical Classification of Diseases and Related
Health Problems (ICD)-9 procedure codes after 1997, for
comparison purposes with our institutional data, isolated
mitral valve procedures were defined as those patients
with no additional valve, coronary or great vessel, or
ablation or electrophysiology procedures.
Methods
Statistical analysis
Subjects were first-time patients for isolated mitral valve
surgery operated upon for different pathologies sampled
Continuous data are presented as mean SD. Categorical data are presented as frequency and percentage. Tests
0268-4705 ß 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins
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100 Valvular heart disease
for significance were accomplished via one-way analysis
of variance (ANOVA), x2 or unconditional logistic
regression where appropriate. All data analysis was
accomplished with SAS (version 9.02; Cary, North
Carolina, USA) and Graphpad Prism (version 4.0; San
Diego, California, USA). P-values less than 0.05 were
considered statistically significant.
Results
Preoperative and clinical characteristics stratified by valve
type can be found in Table 1. Tissue valve patients
generally presented as older, with increased body mass
index, EuroSCORE and creatinine, but experienced
less cross-clamp time compared with mechanical and
repair groups. Tissue valve patients tended to undergo
more elective procedures, be more female, and present
with increased rates of New York Heart Association
(NYHA) class III or IV, history of smoking, diabetes and
arrhythmia.
Institution mitral valve procedure complication trends
The overall operative death rate was 1.3% (bioprosthesis,
3.7%; mechanical, 1.6%; repair, 0.6%). Tissue valve
patients experience a statistically significant increased
LOS compared with the other valve groups (bioprosthesis, 11.8 days; mechanical, 9.3 days; repair, 5.4 days;
P < 0.001). Although not statistically significant, tissue
valve patients experienced increased 30-day mortality
rates [2.4 vs 0.5 (mechanical) or 0.6% (repair)]. Compared
with mitral valve repair, the use of tissue valves increased
the risk of death four-fold [odds ratio (OR) 4.08; 95%
confidence interval (CI) 0.57–29.46], but mechanical
valves were protective (OR 0.86; 95% CI 0.08–9.81).
Age and EuroSCORE were significant confounders for
tissue valves vs repair (OR 2.56; 95% CI 0.30–22.08), but
not mechanical valves vs repair (OR 0.88; 95% CI 0.08–
9.81).
Institution mitral valve procedure trends
Our own experiences of annual mitral valve implantation
rates stratified by type are presented in Fig. 1. The
incidence of mitral valve repair increased steadily
throughout the decade. Beginning with 37.5% in 1996,
mitral valve repair procedures averaged 54.4% from 1996
to 2006 with a high of 78.3% in 2004. By comparison, the
use of mechanical mitral valve procedures decreased
steadily from 52.5% in 1996 to 6.8% in 2006, averaging
31.5% for the time period. Tissue mitral valve procedures
remained relatively constant, averaging 14.0% from 1996
to 2006 with a high of 22.2% in 1997.
National mitral valve procedure trends
Between 1996 and 2005, an estimated 127 671 isolated
mitral valve procedures (37 640 repairs; 90 031 replacements) were performed in the US. Of the 90 031 mitral
valve replacements, 20.9% (n ¼ 18 381) were tissue bioprosthesis. The use of mitral valve repair techniques
increased from a low in 1996 (13.4%) to 55.4% for
2005, the most currently available data. A corresponding
decrease in mechanical valves was observed from 72.2%
in 1996 to 28.2% in 2005.
Annual national estimates of age for patients undergoing a
mitral valve procedure over the decade fluctuated between
61 and 63 years of age, with repair procedures on average
2–3 years younger. Local annual age estimates tended to
be slightly younger than national estimates (58–62 years),
but repair procedures followed the national trend of being
on average 2–3 years younger. When stratified by gender
or age, both male and female patients equally reflected the
national trend, and minimal differences were observed
among the age groups.
Mitral valve procedure trends by gender
Annual institutional and national mitral valve procedure
rates stratified by gender are presented in Fig. 2. Among
Table 1 Clinical and demographic characteristics
Age (mean SD)
Body mass index
Body surface area
EuroSCORE
Creatinine
Cross-clamp time (min)
Female [n (%)]
Elective status
New York Heart Association class (III and IV)
History of smoking
Diabetes
History of coronary artery disease
Cerebrovascular accident
Cerebrovascular disease
Peripheral vascular disease
Myocardial infarction
Arrhythmia
Tissue valve (n ¼ 82)
Mechanical valve (n ¼ 186)
Repair (n ¼ 329)
P-value
63.4 17.1
28.3 31.9
1.8 0.2
8.4 4.7
1.3 1.7
79.5 37.8
50 (60.2)
56 (67.5)
66 (79.5)
36 (43.4)
17 (20.5)
27 (32.5)
10 (12.0)
12 (14.5)
8 (9.6)
10 (12.0)
32 (38.6)
56.8 13.7
26.3 5.6
1.8 0.3
5.4 2.6
0.9 0.3
81.4 36.1
101 (54.3)
101 (54.3)
138 (74.2)
69 (37.1)
13 (7.0)
73 (39.2)
16 (8.6)
16 (8.6)
4 (2.2)
10 (5.4)
62 (33.3)
56.2 12.5
26.6 18.7
1.9 0.2
4.4 2.8
1.0 0.2
88.1 33.3
106 (31.8)
106 (31.8)
143 (42.9)
89 (26.7)
15 (4.5)
128 (38.4)
9 (0.7)
11 (0.3)
5 (1.5)
14 (4.2)
34 (10.2)
0.001
0.691
0.001
0.001
0.001
0.039
0.001
0.001
0.001
0.001
0.001
0.035
0.001
0.001
0.001
0.021
0.001
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Trends in isolated mitral valve surgery Ad et al. 101
Figure 1 Annual implantation rates
Institution
Average 100
National rates
Average 100
80
80
60
60
40
40
20
20
0
0
1997
1999
2001
2003
1997
2005
1999
2001
2003
Year
By valve type, 1996–2006.
Tissue;
mechanical;
2005
Year
repair.
women, from 1996 to 2006, institution female patients
doubled the number of mitral valve repair procedures from
30.0 to 60%, while mechanical mitral valve replacements
decreased from 55.0 to 13.3%. By comparison, male
patients doubled the number of mitral valve repair
procedures from 45.0 to 82.8%, with a subsequent decrease
in mechanical mitral valve replacements from 50.0 to 3.4%.
Over the 4-year period from 2003 to 2006 the use of
mechanical mitral valve procedures among women remai-
ned fairly constant (2003, 29.2%; 2006, 13.3%); among
men, mechanical mitral valve replacements became very
uncommon (2003, 0.0%; 2006, 3.4%). Comparable trends
were seen among national estimates. Among both women
and men, the use of mitral valve repair quadrupled while
the number of mechanical mitral valve replacements
declined by one-half. Currently, approximately 50% of
mitral valve procedures for both women and men are mitral
valve repair (Fig. 2).
Figure 2 Annual implantation rates
Institution female
Average 100
National female
Average 100
80
80
60
60
40
40
20
20
0
0
1997
1999
2001
2003
1997
2005
1999
2001
2003
Year
Institution male
Average 100
2005
Year
National male
Average 100
80
80
60
60
40
40
20
20
0
0
1997
1999
2001
2003
1997
2005
Year
By valve type and gender, 1996–2006.
Tissue;
mechanical;
1999
2001
2003
2005
Year
repair.
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102 Valvular heart disease
Mitral valve procedure trends by age group
Annual mitral valve procedure rates stratified by age
group are presented in Fig. 3.
Mitral valve procedure operative death and length of
stay
Among both age groups, the annual trend towards
increased mitral valve repair was equally distributed across
both age groups. Only among patients aged 65 years or
younger, however, was the annual use of mitral valve tissue
replacement fairly consistent. Among patients older than
65 years, annual rates of mitral valve tissue replacement
fluctuated dramatically. National estimates reflect those
experienced by our institution: stable annual use of
tissue valves as a proportion of mitral valve procedures
among the younger age groups and increased annual use of
tissue mitral valve replacement among patients older than
65 years.
Annual operative death rates following a mitral valve
procedure are presented in Fig. 4. The overall institution
operative death rate was 1.3% (bioprosthesis, 3.7%;
mechanical, 1.6%; repair, 0.6%). Mortality rates were
greatest for all groups among tissue valve replacement
in years 2001 (10.0%), 2002 (16.7%) and 2003 (16.7%),
and as low as 0% in the mitral valve repair group for years
1996–1999, 2001–2002 and 2004–2006. Overall national
mitral valve operative mortality was 5.2% (repair, 2.3%;
bioprosthesis, 8.2%; mechanical, 6.0%). From 1996 to
2005, tissue valves consistently demonstrated the highest
operative mortality rates compared with mechanical or
mitral valve repairs, with current estimates at 3.8% for
bioprosthesis, 3.5% for mechanical and 0.6% for repair.
Among patients aged over 65 years, a distinct pattern
was evident during the last half of the decade. From
1996 to 2001, the use of mitral valve bioprosthesis
replacement procedures remained fairly consistent.
The use of mitral valve repair procedures, however,
increased from one-third (29.2%) of all annual mitral
valve procedures to two-thirds of all annual mitral valve
procedures by 2006 (66.2%), whereas mechanical mitral
valve replacements decreased from 43.5 to 8.8% during
the same time period.
Institution tissue valve patients experienced significantly
increased LOS compared with the other valve groups
(bioprosthesis, 11.8 days; mechanical, 9.3 days; repair, 5.4
days; P < 0.001). Annual average LOS estimates for tissue
valves ranged from a high of 11 days in 2005 to a low of 6
days in 1998, 1999 and 2003. Largest annual
LOS estimates for mechanical and repair were in 2006
(11 days), and 1996, 1997 and 1999–2002 (5 days). Low
annual LOS estimates for mechanical and repair were 5
(1998) and 3 days (2003).
Figure 3 Annual Implantation rates
Institution age < 65
Average 100
National age < 65
Average 100
80
80
60
60
40
40
20
20
0
0
1997
1999
2001
2003
1997
2005
1999
2001
2003
Year
Institution age < 65
Average 100
2005
Year
National age < 65
Average 100
80
80
60
60
40
40
20
20
0
0
1997
1999
2001
2003
1997
2005
Year
By valve type and age group, 1996–2006.
Tissue;
mechanical;
1999
2001
2003
2005
Year
repair.
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Trends in isolated mitral valve surgery Ad et al. 103
Figure 4 Annual operative death and complication rates
Average
Institution operative death
40
Average
30
30
20
20
10
10
0
0
1997
1999
2001
2003
2005
Year
By valve type, 1996–2006.
National operative death
40
Tissue;
mechanical;
1997
1999
2001
2003
2005
Year
repair.
Nationally, annual LOS estimates for tissue, mechanical
and repair procedures were 13.7, 11.8 and 8.2 days,
respectively. Annual LOS estimates for tissue valves
reached a high of 16 days in 1996 and 11 days in 2001.
For mechanical and repair valve procedures, annual LOS
highs were achieved for both in 1996 (14 and 12 days).
Annual LOS lows for mechanical and repair procedures
were seen in 1998 (9 days) and 2005 (7 days).
only one report with ‘Mitral Valve’ and ‘Trends’ concurrently in the title [10]. Northrup et al. [10] experience
similar results to ours: total volume of mitral valve procedures is increasing, which they attribute to the ageing
US population and the ‘baby-boomer’ population wave.
Finally, although the annual volume of mitral valve
procedures is increasing nationally, it appears that the
etiology of mitral valve disease has little to do with postoperative outcomes [11] or with combined procedures
[12,13].
Conclusion
During the past decade, there has been a clear trend in
the volume of mitral valve repairs performed in the US
and our institution. Mitral valve repairs increased from
37.5 to 78.35% of all mitral valve surgery procedures in
our institute and from 13.4 to 55.4% for the US centers.
This occurred without any appreciable change in average
patient age. Mitral valve repair patients presenting for
surgery remain consistently younger and with fewer
comorbidities as compared with tissue or mechanical
valve replacement patients. Although mitral valve repair
procedures demonstrated significantly longer cross-clamp
time compared with replacement procedures, approximately 30% of the mitral valve repairs were done using a
minimally invasive approach, either robotically assisted
or direct. Recent work has documented the superiority
of mitral valve repair vs replacement. Moss et al. [5],
after propensity matching a large cohort of mitral valve
repairs with mitral valve replacements, reported that
mitral valve repair patients experience significantly
increased survival, but tended towards greater rates of
reoperation. Thourani et al. [6] also reported increased
survival of mitral valve repair vs replacement, but concluded that the long-term survival advantage was not
apparent for those patients over 60 years of age.
A comparison of mitral valve procedure trends with
other institutions is difficult. An English language only
MEDLINE search for the years 1966 to 2007 revealed
Several trends are worth noting. Although mitral valve
repair volume doubled from 1996 to 2006 (1996, 37.5%;
2006, 75.0%) with a concurrent constant use of tissue
prosthesis replacement between 2001 and 2006 (2001,
18.5%; 2006, 18.2%), the use of mechanical prosthesis has
diminished significantly to a current use of only 6% of all
mitral valve procedures. Throughout the past decade, our
rate of mitral valve repair among males was 62% compared with 44.1% for women. Since then, the use of mitral
valve repair among men has increased steadily from
45.0% in 1996 to 82.8%, whereas among female patients
the rate of mitral valve repair has increased less rapidly
(30.0% in 1996; 60.0% in 2006). Finally, since 1996 the
use of tissue valves during replacement procedures
among women has remained twice that of men.
Our own perception regarding additional reasons for this
significant change in the practice of mitral valve disease,
especially the trends in the use of mechanical valves, is
directly related to current patient awareness of the negatives surrounding warfarin therapy.
Compared with valve replacement, mitral valve repair
provides lower perioperative morbidity and mortality,
better postoperative left ventricular function, avoidance
of life-long anticoagulation (e.g. coumadin), and
decreased need for repeat surgery due to prosthetic valve
degeneration and bacterial endocarditis.
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104 Valvular heart disease
To summarize, after reviewing our mitral valve surgical
practice for the last decade, several significant observations can be made.
(1) An overall significant change in practice for mitral
valve surgery was observed.
(2) Implantation rates for mechanical valves have
decreased significantly.
(3) Mitral valve repair has become the technique of
choice for mitral valve surgery in our practice, with
increasing numbers of patients being operated using
minimally invasive techniques.
4
Jokinen JJ, Hippelainen MJ, Pitkanen OA, Hartikainen JE. Mitral valve replacement versus repair: propensity-adjusted survival and quality-of-life analysis.
Ann Thorac Surg 2007; 84:451–458.
5
Moss RR, Humphries KH, Gao M, et al. Outcome of mitral valve repair or
replacement: a comparison by propensity score analysis. Circulation 2003;
108:II-90–II-97.
6
Thourani VH, Weintraub WS, Guyton RA, et al. Outcomes and long-term
survival for patients undergoing mitral valve repair versus replacement: effect
of age and concomitant coronary artery bypass grafting. Circulation 2003;
108:298–304.
7
US Census National Population Projections. Current population reports, series
P25-1104, population projections of the united states, by age, sex, race, and
Hispanic origin: 1993 to 2050. Washington: US Census Bureau; 2006.
8
Rosamond W, Flegal K, Friday G, et al. Heart disease and stroke statistics –
2007 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2007; 115:e69–e171.
HCUP Databases. Healthcare cost and utilization project (HCUP). 19962005. Rockville: Agency for Healthcare Research and Quality; 2006.
www.hcup-us.ahrq.gov/databases.jsp.
This document provides detailed information regarding the H-CUP project.
9
References and recommended reading
Papers of particular interest, published within the annual period of review, have
been highlighted as:
of special interest
of outstanding interest
Additional references related to this topic can also be found in the Current
World Literature section in this issue (p. 156).
1 Soltesz EG, Cohn LH. Minimally invasive valve surgery. Cardiol Rev 2007;
15:109–115.
An excellent summary of minimally invasive valve surgery.
10 Northrup WF 3rd, Kshettry VR, DuBois KA. Trends in mitral valve surgery in a
large multisurgeon, multihospital practice, 1979–1999. J Heart Valve Dis
2003; 12:14–24.
11 Shuhaiber J, Anderson RJ. Meta-analysis of clinical outcomes following
surgical mitral valve repair or replacement. Eur J Cardiothorac Surg 2007;
31:267–275.
This important meta-analysis summarizes recent outcomes following mitral valve
procedures.
Winters M, Obriot P. Mitral valve repair. AORN J 2007; 85:152–166.
12 Wong JW, Mak KH. Impact of maze and concomitant mitral valve surgery on
clinical outcomes. Ann Thorac Surg 2006; 82:1938–1947.
3 Rahimtoola SH. The year in valvular heart disease. J Am Coll Cardiol 2007;
49:361–374.
An excellent description of advances in the treatment of heart valve disease.
13 Hassan A, Quan H, Newman A, et al., Canadian Cardiovascular Outcomes
Research Team. Outcomes after aortic and mitral valve replacement surgery
in Canada: 1994/95 to 1999/2000. Can J Cardiol 2004; 20:155–163.
2
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