Another elite athlete develops a shoulder blood clot

I recently published a lengthy blog post about Victor Wembanyama and thoracic outlet syndrome. Three weeks later, the internet is blowing up with news about Philadelphia Phillies ace right-hander Zack Wheeler, who has been diagnosed with a blood clot in the shoulder.

Early news reports on Sunday, August 16, revealed little except for the presence of a blood clot in Wheeler’s throwing shoulder.

ESPN.com:

President of baseball operations Dave Dombrowski said after the Phillies’ 2-0 loss to the Nationals that Wheeler had been diagnosed with a “right, upper extremity blood clot.”

The Athletic:

…a blood clot was found near his right shoulder.

Washington Post:

But the second thing that is true about the blood clot near Wheeler’s throwing shoulder is that the baseball consequences of its emergence could be seismic. The key part of that sentence is “could be” — because the Phillies were clear this weekend that they know very little.

Bleacher Report:

Philadelphia Phillies All-Star starter Zack Wheeler was placed on the 15-day injured list after he was diagnosed with a blood clot near his shoulder, the team announced Saturday…The timetable for Wheeler’s return is “unclear,” per ESPN’s Jeff Passan.

Upper Extremity Blood Clots in Athletes

As I noted in my post regarding Wemby, most mainstream media failed to recognize the significance of this blood clot. Specifically, upper extremity blood clots (also known as DVT, or deep vein thrombosis) comprise only 5% of all blood clots in the body. Within this group, 70% result from cancer, prolonged immobilization, pregnancy, or estrogen use. In essence, 30% of 5% of all patients with blood clots develop these clots without any of the causative factors noted above. This small group is more likely to be younger (37 years old vs. 57 years old), male, and have never had a blood clot elsewhere than the other 70% of upper extremity blood clot patients. In this very specific group, venous thoracic outlet syndrome is THE diagnosis to rule out.

While nearly all of the mainstream media remains focused on the blood clot itself, a few reporters have dug deeper. On Monday, August 17, ESPN.com published an article written by reporter Stephania Bell, ‘Zack Wheeler on IL with blood clot: What it means, what to expect.’ On August 16th, Will Carroll published a substack post, ‘Zack Wheeler Out.’ Let’s look at those in order.

Stephania Bell had put in some serious legwork and presented an excellent initial discussion, including this excerpt:

Blood clots in athletes can be caused by a number of factors. They can occur as the result of direct trauma, resulting in bleeding or swelling that contributes to clot formation. They can follow a period of immobilization (for instance, postsurgery when a limb is immobilized for a period, there can be an increased risk of clot formation). Genetic clotting disorders can be an origin source, but they are rare in an elite athlete.

Bell describes 3 mechanisms that can cause abnormal blood clots. In the 19th century, Rudolf Virchow, known today as the father of modern pathology, described the same 3 factors that can contribute to abnormal blood clot formation. Doctors call this Virchow’s triad:

1. Slow blood flow
2. Damaged blood vessel
3. Abnormal clotting factors in the blood
   

Thus, a post-surgical patient immobilized in bed (slow blood flow), an athlete whose repetitive motion damages a blood vessel over time (damaged blood vessel), or a person who is born with certain inherited abnormalities of blood clotting factors (abnormal clotting factors in the blood) is at increased risk of developing abnormal blood clots.

Upper Extremity Blood Clots Should Raise Concern for Thoracic Outlet Syndrome

Compared to the news cycle that had focused on Victor Wembanyama’s blood clot in isolation, I was pleasantly surprised that reporter Stephania Bell stated the following:

The most likely cause of clot formation in an elite athlete, particularly in the upper extremity of one who repeatedly subjects the arm to overhead stress, is thoracic outlet syndrome.

Thoracic outlet syndrome occurs when the first rib, or occasionally an extra rib, creates compression over the blood vessels and/or nerves as they exit the neck region under the clavicle (collarbone) and travel through the shoulder to the arm and hand. Overhead athletes — most notably, baseball pitchers along with softball players, volleyball players, rowers and swimmers — are most susceptible to clots in the shoulder area due to thoracic outlet syndrome.

The reporter is correct when she states that any pitcher presenting with an upper extremity venous blood clot should be considered to have venous TOS until proven otherwise. However, if one considers all pitchers who develop thoracic outlet syndrome, neurogenic TOS is likely much more common than venous TOS, which is also the case in the general population. In addition, occasional cases of arterial TOS arise in baseball pitchers.

Neurogenic TOS	Venous TOS	Arterial TOS
Matt Harvey	Dillon Gee	Dillon Gee
Chris Young	Zack Wheeler	J. R. Richard
Tyson Ross	Mike Foltynewicz,	David Cone
Josh Beckett	Alex Cobb	Craig Dingman
Kenny Rogers	Aaron Cook	Kip Wells
Stephen Strasburg
Chris Archer
Jaime Garcia
Kenny Rogers
Cole Henry
Jared Walsh
Daniel Bard
Trevor Rosenthal
Drew Verhagen
Josh Beckett

Prognosis for Elite Athletes with Thoracic Outlet Syndrome

Bell moved on to statements regarding prognosis:

With appropriate treatment, athletes have a very high likelihood of returning to their pre-injury level of performance. …In cases where surgery is required, the results have been largely successful in allowing throwers to continue their careers.

The reporter cites former MLB pitchers Matt Harvey, Chris Young, and Dillon Gee as examples of successful surgery for TOS. In fact, these cases argue against the claims of successful surgery. Let’s look at these examples with a more critical mind.

Matt Harvey

Matt Harvey debuted as a pitcher for the New York Mets in 2012. Following the 2013 season, he underwent Tommy John surgery on his throwing elbow, and he missed the 2014 season. Harvey returned in 2015, and took the Mets to the World Series that season. However, the first half of Harvey’s 2016 season was disappointing, and he was diagnosed with neurogenic thoracic outlet syndrome. He underwent rib resection TOS surgery in July of 2016.

Let’s look at some standard and advanced metrics for Matt Harvey’s career.

Matt Harvey	2012 through 2016	2016 through 2021	First 2y After Surgery
ERA	2.95	6.15	3.74
FIP	2.80	5.3	4.32
WHIP	1.084	1.523	1.452
HR/9	0.7	1.7	1.8

The first two columns in this table demonstrate a very big drop-off in Harvey’s performance following TOS surgery. Even when focusing on the first two years following surgery (third column), when we might expect an improvement in performance due to successful treatment of TOS, we find the opposite. Harvey suffered a loss of performance in every one of these statistical metrics.

Chris Young

Chris Young pitched for the Texas Rangers, San Diego Padres, and New York Mets from 2004 through 2012. Young underwent rib resection TOS surgery in 2013, and missed the entire season. He returned to pitch in the major leagues for four more years, from 2014 through 2017.

The reporter noted:

(Young)…signed with the Mariners the following spring and received the American League Comeback Player of the Year award after pitching 165 innings.

Chris Young	Before	After	First 2y After
ERA	3.79	4.31	3.41
FIP	4.24	5.31	4.81
WHIP	1.222	1.339	1.170
HR/9	1.1	1.7	1.3

When comparing standard and advanced baseball statistics for Chris Young’s career before and after TOS surgery, there is a clear loss of performance across the measured categories. Focusing on the first two years following surgery, we do see a mild improvement in ERA and WHIP. However, FIP, which is designed to remove elements of luck for a pitcher, moves in the opposite direction, worse than prior to surgery. At the same time, Young gave up more home runs than prior to surgery. I think it is clear in both the short term and more clearly in the long term, Chris Young performed at a lower level following surgery.

Dillon Gee

Regarding Dillon Gee, ESPN noted:

In 2012, Mets pitcher Dillon Gee… had blood clots — one in his lung that was addressed medically and one in a shoulder artery that was addressed with thrombolysis — and he subsequently underwent surgery to repair the damaged artery.

In fact, Gee’s story is more complex than described here. Gee suffered an arterial blood clot in 2012, and required removal of the clot (thrombolysis), as well as surgery to repair a ‘damaged artery.’ He returned to pitch for the New York Mets and the Kansas City Royals through 2016. Then, in September of 2016, Gee suffered a pulmonary embolism (a blood clot that has traveled to the lungs, blocking blood flow through the lungs), and a venous blood clot was found in his pitching arm. At that time, Gee underwent rib resection TOS surgery. Gee’s case is unusual, as independent blood clots involved different blood vessels, both in his pitching arm, at different times.

Dillon Gee	2010 through 2012	2013 through 2016	2017
ERA	4.36	4.17	3.48
FIP	4.36	4.50	4.77
WHIP	1.406	1.347	1.405
HR/9	1.0	1.3	1.5

Gee’s first surgery in 2012 did not involve removal of rib or scalene muscles. When comparing stats before and after this surgery, ERA and WHIP mildly improved while FIP and home runs per 9 innings worsened somewhat. However, the differences are not striking. When comparing stats before and after rib resection, we see a significant improvement in ERA, but the advanced stats worsen. Importantly, Gee never suffered from the neurogenic type of TOS, which is often harder to diagnose and treat. This factor may have allowed Gee a better recovery than Matt Harvey or Chris Young.

Do Major League Pitchers Come Back from TOS?

There are a good number of other examples of elite pitchers who were diagnosed with TOS, underwent surgery, and attempted a comeback. We have written before about thoracic outlet syndrome in baseball players, the value of advanced baseball statistics in the case of Chris Archer, thoracic outlet syndrome and pitcher effectiveness, and Stephen Strasburg’s attempted comeback from thoracic outlet syndrome.

Strasburg was considered a generational talent. He won the World Series MVP award in 2019 after leading the Washington Nationals to their first championship. Early in the season following his World Series championship, Strasburg suffered from carpal tunnel neuritis, and missed the year following surgery. He returned to pitch in 2021, but was diagnosed with neurogenic TOS. He underwent rib resection TOS surgery, and missed the remainder of that season. Strasburg returned to the mound in June of 2022, but pitched less than 5 innings. Shortly thereafter, he suffered symptoms in his throwing arm, and he never pitched again, retiring in April of 2024.

How Does Zack Wheeler’s Case Compare with other Pitchers’ Cases?

Will Carroll is a sportswriter who specializes in sports injuries and other medical issues in athletes. On August 16, immediately after news of Zack Wheeler’s blood clot broke, Carroll posted on his substack, ‘Zack Wheeler Out.’

Then came the news on Saturday night: a blood clot in his pitching shoulder. For a pitcher, that’s not just a nagging elbow or barking lat. It’s a medical red light, one that carries risks far beyond innings pitched or a team’s playoff hopes.

Blood clots in the shoulder and arm, particularly for pitchers, often fall under a category called Paget–Schroetter syndrome. …Left untreated, that clot can break loose and travel to the lungs. That’s a pulmonary embolism and those can be fatal.

Kudos to Will Carroll for addressing the issue immediately as thoracic outlet syndrome, where the mainstream media had focused solely on the presence of a blood clot. And while he is correct that pulmonary emboli are quite serious, they arise more commonly from blood clots that occur in the lower extremities than from blood clots that occur in the upper extremities.

…If Wheeler’s case follows the path of others before him, it will involve a vascular surgeon, a procedure to remove or dissolve the clot, and can involve the removal of part of the first rib to reduce the compression that caused it in the first place. That’s not minor. It ends seasons. It takes months of rehab but history tells us it doesn’t end careers any more.

Carroll lists several pitchers who had developed upper extremity blood clots and who had first rib resection TOS surgery, then returned to pitch in the major leagues for extended periods. Of note, Dillon Gee, Mike Foltynewicz, Alex Cobb, and Aaron Cook all were diagnosed with and treated for venous thoracic outlet syndrome. Carroll did not compare Wheeler’s case to pitchers with neurogenic thoracic outlet syndrome.

Carroll also pointed out two pitchers, Craig Dingman and Kip Wells, who did not recover from blood clots and surgery. However, each of these pitchers had arterial injuries, and required arterial bypasses. This condition differs from that of Zack Wheeler. In addition, Carroll briefly mentions Chris Bosh, Brandon Ingram, and Victor Wembanyama as further examples, although Chris Bosh did not have upper extremity blood clots.

Later in the post, Carroll specifically refers to TOS:

There’s a useful comparison here to thoracic outlet syndrome (TOS), another vascular compression problem familiar to pitchers. In TOS, nerves and blood vessels get squeezed between the collarbone and first rib. The fix is the same: remove the rib, decompress the area, and hope the arm can relearn its delivery without the same entrapment. Matt Harvey had the surgery in 2016. He never returned to form, his velocity down and command never right, though there were many other issues that contributed. Chris Archer had the rib removal as well and while he did make it back, he was a shadow of his All-Star self.

It is not clear why TOS is described as ‘another vascular compression problem.’ Wheeler’s condition IS TOS. Also, Matt Harvey and Chris Archer suffered from neurogenic TOS, not venous TOS.

Does the Type of Thoracic Outlet Syndrome Affect a Pitcher’s Prognosis?

I have posted several articles regarding baseball pitchers and TOS in general, as well as specific cases such as Chris Archer. In the published literature are a few articles, necessarily based on small sample size, as there are few professional baseball pitchers who develop TOS. I have reservations about several of these articles (I will write on this in the future), and I can only present an educated guess regarding this important question. Please recall that I have investigated standard and advanced baseball statistics in this post and in others.

In my opinion, pitchers who are diagnosed with neurogenic TOS and treated with rib resection are less likely to recover or to return to their prior performance than are pitchers who are diagnosed with venous TOS and successfully treated.

What is Zack Wheeler’s Diagnosis and Prognosis

I am not involved in the care of Zack Wheeler. However, based on limited available information and my experience, it is highly likely that Zack Wheeler has venous TOS. I believe he will proceed to first rib resection TOS surgery, and will miss the remainder of this season. While I know no specifics of his diagnosis, underlying anatomy, or plan of care, the literature appears to show that pitchers with venous TOS can return to their former level of performance in many cases, as opposed to those pitchers with neurogenic TOS or arterial TOS. On the other hand, Zack Wheeler is 35 years old, which may tilt the chances further from complete recovery, given the demands of surgery and extensive rehabilitation. As a physician, I remain moderately hopeful that Zack can make a complete recovery. Of course, as a baseball fan, I wish him a speedy and safe recovery no matter the diagnosis, and hope that he can return to his successful pitching career.

(Editor’s note: As we are going to press on August 23, news is breaking that Zack Wheeler has indeed been diagnosed with TOS, and will undergo surgery to treat the condition.

Philadelphia Phillies ace Zack Wheeler will miss the remainder of the season and is expected to be out for six to eight months after being diagnosed with venous thoracic outlet syndrome, the team announced Saturday.… Venous thoracic outlet… is repaired through surgery, which has been recommended for Wheeler and could allow him to return by Opening Day 2026. The surgery typically entails the removal of a rib to help decompress the area.